Communication Handover Method, Communication Message Processing Method and Program for Executing These Methods by use of a Computer

ABSTRACT

Disclosed is a technique so arranged that, after handover, a mobile terminal can promptly and continuously accept an additional service (for example, QoS assurance), the mobile terminal has accepted before the handover. With this technique, when the mobile terminal (MN  10 ) carries out the handover, the MN selects, as a proxy, a node (QNE (proxy)  68 ) having NSLP for QoS, which exists in the vicinity of an AR (access router)  31  pertaining to a subnet  30  which is a movement destination of the MN (near an AR in a network configuration), and transmits, to this proxy, a message including a flow identifier and a session identifier, which are related to a path  24  established with respect to a CN  60  before the handover. This proxy transmits a message including these flow identifier and session identifier to the CN for, on the basis of a response result to this message, establishing a new path  34  and finding a crossover node at which two paths start to intersect with each other.

TECHNICAL FIELD

The present invention relates to a communication handover method,communication message processing method and a program for executingthese methods by the use of a computer, related to the handover for amobile terminal (mobile node) which carries out radio communications,and more particularly to a communication handover method, communicationmessage processing method and a program for executing these methods bythe use of a computer, related to a mobile node designed to carry outradio communications through the use of a mobile IPv6 (Mobile InternetProtocol version 6) protocol which is a next-generation internetprotocol.

BACKGROUND ART

As a technique capable of offering a connection with a communicationnetwork in a seamless fashion even in the middle of movement to a userwho gains access from a mobile terminal through a radio network to acommunication network such as the internet, a technique utilizing themobile IPv6 establishing a next-generation internet protocol has comeinto widespread use. Referring to FIG. 9, a description will be given ofa radio communication system utilizing this mobile IPv6. A technique onthe mobile IPv6, described hereinbelow, is disclosed in, for example,the following Non-Patent Document 1.

The radio communication system shown in FIG. 9 includes an IP network(communication network) 15 such as the internet, a plurality of subnets(each of which is referred to equally as a subnetwork) 20 and 30connected to the IP network 15, and a mobile terminal (MN : Mobile Node)10 which can make a connection to one of the plurality of subnets 20 and30. In FIG. 9, two subnets 20 and 30 are shown as the plurality ofsubnets 20 and 30.

The subnet 20 is made up of an access router (AR) 21 which conducts therouting with respect to an IP packet (packet data), and a plurality ofaccess points (AP) 22 and 23 establishing unique radio coverage areas(communicable areas) 28 and 29. These APs 22 and 23 are connected to theAR 21, and the AR 21 is connected to the IP network 15. In FIG. 9, twoAPs 22 and 23 are shown as the plurality of APs 22 and 23. Moreover, thesubnet 30 is made up of an AR 31 and a plurality of APs 32 and 33 in thesame connection mode as that of the aforesaid subnet 20.

The AR 21 which is an component of the subnet 20 and the AR 31 which isan component of the subnet 30 are communicable through the IP network15, that is, the subnet 20 and the subnet 30 are connected through theIP network 15.

In the radio communication system shown in FIG. 9, let it be assumedthat the MN 10 has started a radio communication with the AP 23 in theradio coverage area 29. At this time, in a case in which an IPv6 addressallocated to the MN 10 is not suitable for an IP address system of thesubnet 20, the MN 10 existing in the radio coverage area 29 acquires anIPv6 address suitable for the subnet 20, i.e., a care of address (CoA),through a radio communication with respect to the AP 23.

In this connection, as methods for the MN 10 to acquires the CoA, thereare a method of allocating it thereto from a DHCP server in a statefulfashion according to a method such as DHCPv6 and a method in which theMN 10 acquires a network prefix and prefix length of the subnet 20 fromthe AP 21 so as to automatically generate a CoA in a stateless fashionby combining the network prefix and prefix length, acquired from the AR21, and a link layer address or the like of the MN 10.

In addition, the MN 10 registers (Binding Update: BU) the acquired CoAwith respect to a router (home agent) on a home network, to which itpertains, or a specific communication partner (Correspondent Node: CN),thereby enabling the transmission or reception of packet data in thesubnet 20.

Thus, the packet data transmitted from a predetermined communicationpartner to the MN 10 is sent through the AR 21 and the AP 23 to the MN10 on the basis of the CoA of the MN 10, while the packet datatransmitted from the MN 10 to a desired communication counterpart iscommunicated through the AP 23 and the AR 21 to the aforesaid desiredcommunication partner. Moreover, on the basis of the CoA of the MN 10registered in a home agent, the packet data addressed to the MN 10transmitted to the home network is also sent to the AR 21 of the subnet20 and communicated through the AP 23 to the MN 10.

As described above, in the radio communication system using the mobileIPv6 shown in FIG. 9, even in a case in which the MN 10 makes thehandover from one subnet to a different subnet, the employment of theCoA enables the radio communication of the MN 10 to continue. As atechnique for achieving the speeding-up of this handover processing, forexample, there has been known a fast handover technique disclosed in thefollowing Non-Patent Document 2.

According to this fast handover technique, before the MN 10 carries outthe L2 handover, the MN 10 can previously acquire a new CoA (hereinafter referred to as NCoA) to be used in the subnet 30 to generate atunnel between the AR 21 and the AR 31 when the NCoA is notified to theAR 21, and the MN 10 shifts to the subnet 30 after carrying out the L2handover for conducting the connection switching from the AP 23 to theAP 32 and, even for the duration until the previously acquired NCoA isregistered (BU) formally, the packet data sent to an old (Previous) CoA(hereinafter referred to as PCoA) of the MN 10, which has been used inthe subnet 20, is transferred by way of the tunnel and through the AR 31and the AP 32 to the MN 10, and the packet data transmitted from the MN10 arrives at the AR 21 by way of the tunnel and through the AP 32 andthe AR 31 and it is transmitted from the AR 21 to a communicationpartner.

On the other hand, in a communication using a network, a serviceincluding a QoS (Quality of Service) assurance (in this specification,such a service will be referred to as an additional service) exists andvarious types of communication protocols exists for realizing such anadditional service. Of these various types of communication protocols,as a protocol for the QoS assurance, for example, there exists an RSVP(Resource Reservation Protocol) (for example, see the followingNon-Patent Document 3). The RSVP is for making a band reservation on apath (flow) from a transmission side communication terminal, whichconducts data transmission, to a reception side communication terminal,which makes data reception, so that data is smoothly transmitted fromthe transmission side communication terminal to the reception sidecommunication terminal.

Although there is a need for the MN 10 which carries out the handoverbetween the subnets 20 and 30 to, even after the handover,uninterruptedly receive an additional service including a QoS assurancewhich has received before the handover, the above-mentioned RSVP cannotsatisfy the foregoing requirements particularly in the following pointsand cannot cope with the movement of the MN 10. FIG. 10 is anillustrative view for explaining the fact that an RSVP according to aconventional technique cannot cope with the movement of an MN.

In the RSVP, a QoS path is set in a path between two points (end-to-endpath) from a communication partner terminal (CN: Correspondent Node) 60relative to the MN 10, and data transfer is made through the use of aplurality of repeater nodes 61, which make connections for theend-to-end path, on the basis of the addresses of the MN 10 and the CN60. Therefore, for example, in a case in which the MN 10 conducts thehandover between the subnets 20 and 30 and the CoA of the MN 10 ischanged, although there is a need to, in the QoS path, carry out theprocessing related to an address change in addition to a flow change,the RSVP cannot handle such changes, which consequently breaks the QoSassurance (first problem: difficulty is experienced in changing the QoSpath). Moreover, even in a case in which a QoS path is newly set, if anoverlapping portion occurs between the QoS paths before and after thehandover, there is a possibility that a double resource reservation(double reservation) arises in this overlapping portion (second problem:double resource reservation).

For solving the above-mentioned problems, at present, in the IETF(Internet Engineering Task Force), a discussion has been made for thepurpose of standardizing a new protocol referred to as an NSIS (NextStep in Signaling) (see the be particularly effective to various typesof additional services including a QoS assurance in mobile environmentsand, with respect to the NSIS, there are documents (for example, see thefollowing Non-Patent Documents 5 to 9) which describe the requirementsfor realizing a QoS assurance and mobility supports, realizationmethods, and others. A description will be given hereinbelow of theoutline of the NSIS which is presently a draft specification in an NSISworking group of the IETF, and a method of establishing a QoS path (seeNon-Patent Document 6 and Non-Patent Document 9).

FIG. 11 shows an NSIS and a lower protocol stack relative thereto forexplaining a protocol arrangement of the NSIS according to aconventional technique. An NSIS protocol layer is positioned immediatelyabove IP and lower layers. Moreover, the NSIS protocol layer is composedof two layers: an NSLP (NSIS Signaling Layer Protocol) which is aprotocol for generating a signaling message to offer each additionalservice and for conducting the processing therefor, and an NTLP (NSISTransport Layer Protocol) for carrying out the routing on a signalingmessage of the NSLP. As the NSLPs, there are various NSLPs such as anNSLP (QoS NSLP) for QoS, an NSLP (NSLP for a service A, NSLP for aservice B) for one different additional service (service A or serviceB), and others.

Moreover, FIG. 12 is an illustrative view for explaining the conceptthat NEs or QNEs which are nodes of the NSIS according to a conventionaltechnique “adjacent”. As shown in FIG. 12, at least an NTLP is mountedin each of all the nodes (NE: NSIS Entity) having an NSIS function.There is no need to always place an NSLP on the NTLP, and it is alsoacceptable that one or more NSLPs exist. In this case, an NE having anNSLP for QoS will be particularly referred to as a QNE (QoS NSISEntity). A device capable of becoming an NE is a terminal or a router.Still moreover, a plurality of router but NE can exist between theadjacent NEs, and pluralities of routers, but NE, and NEs, each of whichdoes not have a QoS NSLP, can exist between the adjacent QNEs.

With reference to FIG. 13, a description will be given herein below ofone example of a conventional QoS path establishing method. Let it beassumed that the MN 10 connected to the AR 21 in the subnet 20 isscheduled to receive data from an CN 60 or is receiving it therefrom (inreception). When establishing a QoS path (path 24), the MN 10 transmitsa RESERVE message for the establishment of the QoS path toward the CN60. The RESERVE message includes information (QSpec) on a desired QoSfor the data reception from the CN 60. The transmitted RESERVE messagepasses through an AR 21, an NE 62 and a different router, which does nothave an NSIS function, and arrives at a QNE 63. The NSLP of the QNE 63reserves a QoS resource, described in a QSpec included in the RESERVEmessage, for this session. The RESERVE message after passing through theQNE 63 reaches a QNE 65 by way of an NE 64 and a different router whichdoes not have an NSIS function. Also in the QNE 65, the processing isconducted as in the case of the QNE 63 so as to reserve a QoS resource.This operation is repeated and the RESERVE message is finally deliveredto the CN 60, thereby establishing a QoS path between the MN 10 and theCN 60.

In addition, a flow identifier and a session identifier are used foridentifying the resource reservation. The flow identifier depends uponthe CoA of the MN 10 or the IP address of the CN 60, and each of theQNEs 63 and 65 can confirm the IP address of the source/destination ofeach data packet so as to learn the presence or absence of the resourcereservation with respect to this data packet. In this connection, in acase in which the MN 10 moves to a different subnet so that the CoAchanges, a flow identifier changes according to the change of the CoA ofthe MN 10. On the other hand, the session identifier is for identifyinga series of data transmission for a session, and it does not changeaccording to the movement of a terminal unlike the flow identifier.

Still additionally, as a method of examining the possibility ofacquisition of a QoA resource with respect to an arbitrary path, thereis a method referred to as QUERY. This method is, for example, a methodof, when the MN 10 establishes a QoS path with respect to the CN 60,previously making an examination as to whether or not a desired QSpeccan make a reservation in each QNE, and a QUERY message is transmittedfor examining whether or not a desired QSpec can make a reservation ineach QNE and the result thereof is receivable by a RESERVE message whichis an response to the QUERY message. The present resource reservationstate is not changed by these QUERY and RESERVE messages at all.Moreover, when a QNE makes some notification to a different QNE, aNOTIFY message is available. For example, this NOTIFY message is usedfor the error notification or the like. Each of the above-mentionedRESERVE, QUERY, RESPONSE and NOTIFY messages is an NSLP message for theQoS assurance and is written in the Non-Patent Document 6.

Furthermore, referring to FIG. 14, a description will be given of amethod according to a conventional technique, which is for avoiding adouble resource reservation when the MN 10 moves from the subnet 20 tothe subnet 30. When the MN 10 is receiving data from the CN 60 and a QoSpath (path 24) is established, a QoS resource desired by the MN 10 isreserved in a QNE 63, a QNE 65 and a QNE 66. At this time, a flowidentifier and a session identifier are taken as X and Y, respectively.In fact, as mentioned above, the flow identifier X includes the presentIP address of the MN 10 and the IP address of the CN 60, while asufficiently large arbitrary numeric value is set in the sessionidentifier Y. In this state, after moving to the subnet 30, the MN 10sends a RESERVE message to the CN 60 for establishing a new QoS path.Incidentally, the old path (path 24) is not released immediately afterthe movement of the MN 10.

Since the flow identifier changes according to the movement of the MN 10as mentioned above, the flow identifier X in the path 24 and the flowidentifier in the path 34 (the flow identifier in this path 34 is takenas Z) differ from each other. Since a QNE 67 does not have are sourcereservation for the session identifier Y in all interfaces, a decisionis made that a new path is established, and a resource reservation ismade with respect to the flow identifier Z and the session identifier Y.On the other hand, a resource reservation with respect to the sessionidentifier Y exists in the QNE 65 and the QNE 66. Each of the QNE 65 andthe QNE 66 makes a comparison on the flow identifier and confirms thechange of the flow identifier from X to Z and makes a decision that anew path is established due to the movement of the MN 10 so as to, foravoiding the double resource reservation, take a measure such asupdating the old reservation without reserving a resource newly. The QNEat which the old path and the new path starts to intersect with eachother is referred to as a CRN (Crossover node). Although the CRNsometimes signifies a router (NE 64 in FIG. 14) at which the pathsactually start to intersect with each other, in the case of a discussionon the QoS path, the CRN signifies a QNE (QNE 65 in FIG. 14) having astate that, in the old path (path 24) and the new path (path 34), oneadjacent QNE (QNE 66 in FIG. 14) is the same while the other adjacentQNE (QNE 63 or QNE 67 in FIG. 14) varies.

Furthermore, according to the Non-Patent Document 6 or the Non-PatentDocument 9, with respect to these RESERVE message, QUERY message andNOTIFY message, in addition to an end terminal (MN 10 or CN 60) whichforms the source or destination of the packet data, an arbitrary QNE canbecome the source.

Although the NSIS covers various functions in normal static networks inaddition to mobile environments, in this specification, taking note of afunction to realize the establishment of a mobility-supported additionalservice which is one of the functions of the NSIS, the establishment ofa mobility-supported additional service is realized by mounting theNSIS.

-   Non-Patent Document 1: D. Johnson, C. Perkins and J. Arkko,    “Mobility Support in IPv6”, draft-ietf-mobileip-ipv6-24, June 2003-   Non-Patent Document 2: Rajeev Koodli “Fast Handovers for Mobile    IPv6”, draft-ietf-mobileip-fast-mipv6-08, October 2003-   Non-Patent Document 3: R. Braden, L. Zhang, S. Berson, S. Herzog    and S. Jamin, “Resource ReSerVation Protocol-Version 1 Functional    Specification”, RFC 2205, September 1997-   Non-Patent Document 4: NSIS WG    (http://www.ietf.org/html.charters/nsis-charter.html)-   Non-Patent Document 5: H. Chaskar, Ed, “Requirements of a Quality of    Service (QoS) Solution for Mobile IP”, RFC3583, September 2003-   Non-Patent Document 6: Sven Van den Bosch, Georgios Karagiannis and    Andrew McDonald “NSLP for Quality-of Service signalling”,    draft-ietf-nsis-qos-nslp-01.txt, October 2003-   Non-Patent Document 7: X. Fu, H. Schulzrinne, H. Tschofenig,    “Mobility issues in Next Step signaling,    draft-fu-nsis-mobility-01.txt, October 2003-   Non-Patent Document 8: Roland Bless, et. Al., “Mobility and Internet    Signaling Protocol”,    draft-manyfolks-signaling-protocol-mobility-00.txt, January 2004-   Non-Patent Document 9: R. Hancock (editor), “Next Steps in    Signaling: Framework”, draft-ietf-nsis-fw-05.txt, October 2003-   In FIG. 14, for example, we see about a situation that the MN 10    accepting a QoS assurance in the subnet 20 to which it has made a    connection before the handover carries out the handover to the    subnet 30 and continuously receives the QoS assurance, it has    received before the handover, in the subnet 30 to which it makes a    connection after the handover.

In this case, the time to be taken from when the MN 10 hands off thesubnet 20 connected before the handover until the MN 10 comes into astate accepting an additional service (in this case, QoS assurance) inthe subnet 30 connected after the handover is a period of time for whichthe MN 10 cannot accept the QoS assurance, and the MN 10 cannot acceptthe QoS assurance at all, or the default QoS transfer processingconsequently takes place, which breaks the QoS.

Accordingly, as mentioned above, there is a need to promptly offer theQoS assurance to the MN 10 after the handover. For solving this, in thepresent discussion (for example, Non-Patent Document 7) on the NSIS inthe IETF, for example, there exist the proposals to the effect that somepreparation is required in order to establish a new QoS path before theMN 10 conducts the handover or before the MN 10 terminates the handover,and that there is a need to establish a new QoS path in advance.However, although these proposals are merely made, a concreterealization method is not disclosed at all. Moreover, although there isa need to previously find the aforesaid CRN as a preparation forestablishing a new path, a concrete realization method is not disclosedwith respect to this point.

In addition, as another problem, we see about a case in which, when aQoS resource reservation for the communication from the MN 10 to the CN60 exists on the path 24, for example, the MN shifts to the subnet 30where it carries out QUERY with respect to the CN 60. In this case,since, as mentioned above, the resource reservation for thecommunication between the MN 10 and the CN 60 on the path 24 is notreleased for some time after the movement of the MN 10, the resourcereservation for the communication between the MN 10 and the CN 60 on thepath 24 is left for some time in the QNE 65 and the QNE 66. Difficultyis experienced in returning it as a free resource to the MN 10 (usingfor a new path after the movement of the MN 10), which consequentlymakes it difficult for the MN 10 to accurately obtain vacancyinformation on the resource. This problem also applies to not only thecase in which the MN 10 after the movement issues a request through aQUERY message but also a case in which, for example, an arbitrary QNE(for example, QNE 67) on the path 34 transmits a request through theQUERY message.

DISCLOSURE OF THE INVENTION

In consideration of the above-mentioned problems, it is an object of thepresent invention to provide a communication handover method,communication message processing method and program for executing thesemethods by the use of a computer, which enable a mobile terminal, whichconducts handover, to promptly and continuously accept an additionalservice, the mobile terminal has accepted before the handover, after thehandover.

For achieving the above-mentioned purpose, a communication handovermethod according to the present invention for a mobile terminal soarranged as to, in a communication system in which a plurality of accessrouters each constituting a subnet are connected through a communicationnetwork and at least one access point forming a unique communicable areais connected to each of the plurality of access routers, make acommunication with the access router, to which the access point isconnected, through a radio communication with the access point in thecommunicable area, comprises:

a reception step of, when the mobile terminal makes communicationswitching from an access point which is presently in communication to adifferent access point, receiving information on the different accesspoint from the different access point,

an information acquiring step of, when the communication switching ismade to the different access point, acquiring information on a routercapable of making a preparation related to an additional service, themobile terminal desires, after the communication switching on the basisof the information on the different access point received in thereception step, and

an information transmitting step of generating a message includinginformation on the additional service presently in acceptance during thecommunication and, on the basis of the information on the router capableof making the preparation related to the additional service after thecommunication switching, sending the message through the access point,which is presently in communication, to the router capable of making thepreparation related to the additional service after the communicationswitching.

With the above-mentioned arrangement, before the mobile terminal carriesout the communication switching between the access points, theprocessing is conducted so as to continuously accept the additionalservice currently in acceptance (before the communication switching)even after the communication switching, so the mobile terminal, whichcarries out the handover, can continuously and promptly accept theadditional service, the mobile terminal has accepted before thehandover, after the handover.

In addition to the above-mentioned arrangement, the communicationhandover method according to the present invention comprises a storagestep in which the mobile terminal stores, in predetermined informationstoring means of the mobile terminal, correspondence informationdescribing correspondence relationship between the information on theaccess point and the information on the router capable of making thepreparation related to the additional service after the communicationswitching.

With the aforesaid arrangement, the mobile terminal can hold theinformation on the router capable of making the preparation related tothe additional service after the communication switching in a stateassociated with the information on the access point.

In addition to the above-mentioned arrangement, the communicationhandover method according to the present invention is so arranged that,in the aforesaid information acquiring step, the information on therouter capable of making the preparation related to the additionalservice after the communication switching and associated with theinformation on the different access point is acquired from thecorrespondence information on the basis of the information on thedifferent access point received in the reception step.

With the above-mentioned arrangement, when the information becomesreceivable from an access point different from the access pointcurrently in communication, on the basis of the received access pointinformation, it is possible to find an optimum router for making thepreparation related to the additional service after the communicationswitching.

Furthermore, for achieving the above-mentioned purpose, a communicationhandover method according to the present invention for a mobile terminalso arranged as to, in a communication system in which a plurality ofaccess routers each constituting a subnet are connected through acommunication network and at least one access point forming a uniquecommunicable area is connected to each of the plurality of accessrouters, make a communication with the access router, to which theaccess point is connected, through a radio communication with the accesspoint in the communicable area, comprises:

a reception step of, when the mobile terminal makes communicationswitching from an access point which is presently in communication to adifferent access point, receiving information on the different accesspoint from the different access point, and

an information transmitting step of generating a message including theinformation on the different access point received in the reception stepand information on an additional service presently in acceptance duringthe communication and, on the basis of the information on the accesspoint, transmitting the message through the access point presently incommunication to a predetermined server capable of acquiring informationon a router capable of, when communication switching is made to thedifferent access point, making a preparation related to the additionalservice, the mobile terminal desires, after the communication switching.

With the above-mentioned arrangement, the mobile terminal offers theinformation on the additional service currently in acceptance to thepredetermined server capable of acquiring the information on the routercapable of making the preparation related to the additional serviceafter the communication switching, which enables the processing forcontinuously receiving the additional service currently in receptionafter the access point communication switching so that the mobileterminal, which carries out the handover, can promptly and continuouslyreceive the additional service, which has been received before thehandover, after the handover.

Furthermore, for achieving the above-mentioned purpose, a communicationhandover method according to the present invention for a mobile terminalso arranged as to, in a communication system in which a plurality ofaccess routers each constituting a subnet are connected through acommunication network and at least one access point forming a uniquecommunicable area is connected to each of the plurality of accessrouters, make a communication with the access router, to which theaccess point is connected, through a radio communication with the accesspoint in the communicable area, comprises:

an information transmitting step of generating a message including theinformation on an additional service presently in acceptance during thecommunication and, when the mobile terminal carries out communicationswitching from an access point presently in communication to a differentaccess point, transmitting the message through the access pointpresently in communication to all predetermined routers each capable ofrealizing the additional service after the communication switching andselected by the mobile terminal.

With the above-mentioned arrangement, for example, a message includingthe information on the additional service presently in reception duringthe communication is transmitted to a predetermined router having afunction to realize the additional service the mobile terminal grasps inadvance, thereby conducting the processing for continuously receivingthe additional service currently in acceptance after the access pointcommunication switching so that the mobile terminal, which carries outthe handover, can promptly and continuously accept the additionalservice which has been accepted before the handover.

In addition to the above-mentioned arrangement, the communicationhandover method according to the present invention further comprises:

a step in which the mobile terminal specifies an access router havingthe different access point as a following on the basis of theinformation on the different access point received in the receptionstep,

a step of acquiring information on the access router having thedifferent access point as a following, and

an address generating step of generating address information availablein the subnet, to which the access router pertains, on the basis of theinformation on the access router having the different access point as afollowing.

With the above-mentioned arrangement, the mobile terminal can carriesout the stateless automatic setting of the address information.

Moreover, in addition to the above-mentioned arrangement, in thecommunication handover method according to the present invention, in theinformation transmitting step, the message is transmitted in a statewhere the address information generated in the address generating stepis included in the message.

With the above-mentioned arrangement, the mobile terminal can transmit,as one message, the information on the additional service currently inreception during the communication and the address information generatedby the stateless automatic setting.

Still moreover, in addition to the above-mentioned arrangement, in thecommunication handover method according to the present invention, theadditional service is a QoS assurance.

With the above-mentioned arrangement, also after the handover, themobile terminal, which carries out the handover, can promptly andcontinuously accept the QoS assurance that has been accepted before thehandover.

Yet moreover, according to the present invention, there is provided acommunication handover program for executing the above-describedcommunication handover methods through the use of a computer.

Furthermore, for achieving the above-mentioned purpose, a communicationmessage processing method according to the present invention for arouter provided in a communication system so arranged that a pluralityof access routers each constituting a subnet are connected through acommunication network and at least one access point forming a uniquecommunicable area is connected to each of the plurality of accessrouters and a mobile terminal existing in the communicable area makes acommunication with the access router, to which the access point isconnected, through a radio communication with the access point, with therouter being capable of making a preparation related to an additionalservice, the mobile terminal desires, after communication switching whenthe mobile terminal switches the communication with the access point,comprises:

a first information receiving step of receiving, from the mobileterminal, a message including information on the additional service themobile terminal presently accepts during the communication,

a step of generating a message for a preparation of the additionalservice on the basis of the information on the additional service,

a terminal specifying step of specifying a partner terminal, with whichthe mobile terminal presently makes a communication, on the basis of theinformation on the additional service the mobile terminal presentlyaccepts during the communication,

an information transmitting step of generating a message for acquiringinformation, which enables the preparation related to the additionalservice after the communication switching, on the basis of theinformation on the additional service the mobile terminal presentlyaccepts during the communication, and transmitting the message to thepartner terminal, and

a second information receiving step of receiving a message including theinformation, which enables the preparation related to the additionalservice after the communication switching, from the partner terminal orfrom an arbitrary node lying on a path of the message to the partnerterminal.

The above-mentioned arrangement enables the processing to be conductedbefore the mobile terminal carries out the access point communicationswitching, for continuously receiving the additional service currentlyin acceptance (before the communication switching) after the accesspoint communication switching so that the mobile terminal, which carriesout the handover, can promptly and continuously accept the additionalservice, the mobile terminal has accepted before the handover, thehandover.

Still furthermore, in addition to the above-mentioned arrangement, thecommunication message processing method according to the presentinvention comprises a storage step of storing the information, whichenables the preparation related to the additional service after thecommunication switching, received from the partner terminal or from thearbitrary node lying on the path of the message to the partner terminalin the second information receiving step.

With the above-mentioned arrangement, the router which has received themessage including the information on the additional service, the mobileterminal presently accepts during the communication, from the mobileterminal can grasp the information on a path leading to the partnerterminal and preserve this information.

Yet furthermore, in addition to the above-mentioned arrangement, thecommunication message processing method according to the presentinvention comprises a step of generating a message including theinformation, which enables the preparation related to the additionalservice after the communication switching, received from the partnerterminal in the second information receiving step to transmit themessage to the mobile terminal.

With the above-mentioned arrangement, the router which has received themessage including the information on the additional service, the mobileterminal presently accepts during the communication, from the mobileterminal can acquire the information which enables the preparationrelated to the additional service after the communication switching, andthen notify it to the mobile terminal.

Moreover, in addition to the above-mentioned arrangement, thecommunication message processing method according to the presentinvention comprises a step of verifying the validity of the addressinformation when address information usable by the mobile terminal inthe subnet, to which the access router pertains, is included in themessage received from the mobile terminal, which does not exist in thesubnet to which the access router pertains, in the first informationreceiving step, and

a step of, when the validity of the address information is grasped,previously establishing a path for the additional service, the mobileterminal accepts after the communication switching, on the basis of theaddress information.

With the above-mentioned arrangement, the establishment of the path forthe additional service requires the address information on the mobileterminal and, for example, when the validity of the address informationgenerated through the stateless automatic setting is grasped by themobile terminal, it is possible to previously establish a path for theadditional service related to the mobile terminal.

In addition, for achieving the above-mentioned purpose, a communicationmessage processing method according to the present invention for a nodeor a router provided in a communication system so arranged that aplurality of access routers each constituting a subnet are connectedthrough a communication network and at least one access point forming aunique communicable area is connected to each of the plurality of accessrouters and a mobile terminal existing in the communicable area makes acommunication with the access router, to which the access point isconnected, through a radio communication with the access point, and madeto constitute a path related to an additional service when the mobileterminal makes a communication with a predetermined communicationterminal, comprises:

a reservation judging step of, upon receipt of a message including aflow identifier and a session identifier, related to a predeterminedpath, for checking whether the predetermined path is set or not, makinga judgment as to whether or not a resource reservation is made withrespect to the flow identifier and the session identifier included inthe message, and

a step of transmitting a message including a result of the judgment inthe reservation judgment step to a source or destination of the messagefor checking whether the predetermined path is set or not.

With the above-mentioned arrangement, upon receipt of the messageincluding the flow identifier and the session identifier related to thepredetermined path for checking whether the predetermined path is set ornot, the node or the router can make a judgment as to whether a resourcereservation is made with respect to the flow identifier and the sessionidentifier, so as to return a result thereof to a predetermined sourceor destination related to the message.

Still additionally, for achieving the above-mentioned purpose, acommunication message processing method according to the presentinvention for a node or a router provided in a communication system soarranged that a plurality of access routers each constituting a subnetare connected through a communication network and at least one accesspoint forming a unique communicable area is connected to each of theplurality of access routers and a mobile terminal existing in thecommunicable are a makes a communication with the access router, towhich the access point is connected, through a radio communication withthe access point, and made to constitute a path related to an additionalservice when the mobile terminal makes a communication with apredetermined communication terminal, comprises:

a reservation judging step of, upon receipt of a message including aflow identifier and a session identifier, related to a predeterminedpath, for checking whether the predetermined path is set or not, makinga judgment as to whether or not a resource reservation is made withrespect to the flow identifier and the session identifier included inthe message, and

a transfer step of, when a judgment in the reservation judging stepshows that the resource reservation is made with respect to said flowidentifier and said session identifier included in said message, addingaddress information on an interface used for there source reservation toa predetermined portion of the message and transferring the message.

With the above-mentioned arrangement, it is possible that the node orthe router, which has received the message including the flow identifierand the session identifier, related to the predetermined path, forchecking whether the predetermined path is set or not, makes a decisionas to whether or not a resource reservation has been made with respectto the flow identifier and the session identifier and, if the resourcereservation has taken place, inserts the address information on its owninterface related to the resource reservation into the message andtransfers this message, which enables specifying the node or the route,which has the resource reservation on the path, for example, byreferring to the contents of the message.

Yet additionally, in addition to the above-mentioned arrangement, in thecommunication message processing method according to the presentinvention, the predetermined portion indicates an adding sequence of theinterface address information.

The above-mentioned arrangement enables the disposition of the nodes orthe routers in the path to be estimated from the adding sequence of theinterface addresses.

Moreover, for achieving the above-mentioned purpose, a communicationmessage processing method according to the present invention for acommunication node designed to, in a communication system in which aplurality of access routers each constituting a subnet are connectedthrough a communication network and at least one access point forming aunique communicable area is connected to each of the plurality of accessrouters, make a communication with a mobile terminal so arranged as tomake a communication with the access router connected to the accesspoint through a radio communication with the access point in thecommunicable area and designed to be capable of establishing a pathrelated to an additional service when making a communication with themobile terminal, comprises:

a step of, upon receipt of a message including a flow identifier and asession identifier, related to a predetermined path, for seeking thepredetermined path, generating a new message including a result of theseeking of the predetermined path in the message to transmit the newmessage as a response to the message.

The above-mentioned arrangement enables the message for seeking the pathfor the additional service established, for example, between the mobileterminal and a partner terminal to be transmitted to the partnerterminal so that a message including a seek result the message collectsis returned as a response.

Still moreover, in addition to the above-mentioned arrangement, in thecommunication message processing method, the message for checkingwhether the predetermined path is set or not, or the message for seekingthe predetermined path is a QUERY message or a RESPONSE message havingan area capable of including a flow identifier and a session identifierwhich are related to the path.

This enables the information on the predetermined path to be acquiredthrough single transmission/reception of the message by the use of theQUERY message and the RESPONSE message existing so far.

Yet moreover, in addition to the above-mentioned arrangement, in thecommunication message processing method, the message for checkingwhether the predetermined path is set or not, or the message for seekingthe predetermined path has an area capable of including information on afree resource.

The above-mentioned arrangement enables grasping the information on afree resource (for example, release situation of a resource) and othersthrough the aforesaid message.

In addition, a communication message processing method according to thepresent invention for a node or a router provided in a communicationsystem so arranged that a plurality of access routers each constitutinga subnet are connected through a communication network and at least oneaccess point forming a unique communicable area is connected to each ofthe plurality of access routers and a mobile terminal existing in thecommunicable area makes a communication with the access router, to whichthe access point is connected, through a radio communication with theaccess point, and made to constitute a path related to an additionalservice when the mobile terminal makes a communication with apredetermined communication terminal, comprises:

a reservation judging step of, upon receipt of a message including asession identifier related to a predetermined path for checking whetherthe predetermined path is set or not, making a judgment as to whether ornot a state exists with respect to the session identifier, and

a transmission step of, when the reservation judging step shows that thestate does not exist with respect to the session identifier,transmitting the message to the predetermined communication terminal.

With the above-mentioned arrangement, the mobile terminal transmits, ina direction of a partner terminal, the message for seeking the path forthe additional service established between the mobile terminal and thepartner terminal, and this message does not reach the partner terminaland the detection of a crossover node becomes feasible, thus enablingthe detection of the crossover node more promptly.

Still additionally, a communication message processing method accordingto the present invention for a node or a router provided in acommunication system so arranged that a plurality of access routers eachconstituting a subnet are connected through a communication network andat least one access point forming a unique communicable area isconnected to each of the plurality of access routers and a mobileterminal existing in the communicable area makes a communication withthe access router, to which the access point is connected, through aradio communication with the access point, and made to constitute a pathrelated to an additional service when the mobile terminal makes acommunication with a predetermined communication terminal, comprises:

a reservation judging step of, upon receipt of a message including asession identifier related to a predetermined path for checking whetherthe predetermined path is set or not, making a judgment as to whether ornot a state exists with respect to the session identifier,

a reservation judging step of, upon receipt of a message includingidentification information for specifying a flow and a sessionidentifier related to a predetermined path for checking whether thepredetermined path is set or not, making a judgment as to whether or nota state exists with respect to the flow specifying identificationinformation, and

a judgment step of, when the reservation judging step shows that thestate exists with respect to the session identifier, making a judgmentas to whether or not a different adjacent node or router is specified ineach of the state and the message, and

a CRN judging step of, when the judgment step shows that the adjacentnode or router is specified, making a judgment that it is a crossovernode.

With the above-mentioned arrangement, the mobile terminal transmits, ina direction of a partner terminal, the message for seeking the path forthe additional service established between the mobile terminal and thepartner terminal, and this message does not reach the partner terminaland the detection of a crossover node becomes feasible, thus enablingthe detection of the crossover node more promptly.

Yet additionally, in addition to the above-mentioned arrangement, thecommunication message processing method comprises a notification stepof, when the CRN judging step shows that it is a crossover node, issuinga notification to the effect that it is a crossover node, to apredetermined node.

With the above-mentioned arrangement, a notification on a crossoverpoint can be made to, for example, a node functioning as a proxy or thelike.

Moreover, in addition to the above-mentioned arrangement, thecommunication message processing method comprises a step of, in a statewhere the node or the router constituting the path related to theadditional service has a flow identification list for storing thecorrespondence relationship between each resource and information forspecifying a flow, adding or deleting the flow specifying information onthe path related to the additional service, which goes through it, Torofrom the flow identification list.

With the above-mentioned arrangement, the node or the router which is acomponent of the path related to the additional service can grasp thecorrespondence relationship between the resource and the information forspecifying the flow.

Still moreover, in addition to the above-mentioned arrangement, thecommunication message processing method comprises an updating step of,when the CRN judging step shows that it is a crossover node,transmitting, to the communication terminal, a message for addinginformation, which is for specifying a new flow, to the flowidentification list in which the resource for the predetermined path isallocated with respect to each receiving node or router.

The above-mentioned arrangement enables promptly carrying out a changeof a resource allocation at an overlapping portion between the new andold paths, two in number.

Yet moreover, according to the present invention, there is provided acommunication message processing program for executing theabove-mentioned communication handover methods through the use of acomputer.

The present invention provides the communication handover methods,communication message processing methods and programs for executingthese methods through the use of a computer, which have the arrangementsdescribed above, and provides an effect that a CRN is found in advance(before the handover or immediately after the handover) so that, evenafter the handover, a mobile terminal which carries out the handover canpromptly and continuously accept an additional service it has acceptedbefore the handover. In addition, in a case in which a terminal whichhas conducted the handover or an agency router (proxy) for a terminal inmovement carries out QUERY for acquiring information on a new path, itis possible to return correct information while considering a resourcereservation situation before the movement of an MN between a CRN and aCN.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustrative view showing a configuration of acommunication system according to an embodiment of the presentinvention;

FIG. 2 is a block diagram showing a configuration of an MN in anembodiment of the present invention;

FIG. 3 is a block diagram showing a configuration of a proxy in anembodiment of the present invention;

FIG. 4 is a block diagram showing a configuration of a QNE in anembodiment of the present invention;

FIG. 5 is a block diagram showing a configuration of a CN in anembodiment of the present invention;

FIG. 6 is an illustrative view showing one example in which informationprocessed by a QNE is to be stored in a message to betransmitted/received by a proxy and a CN in an embodiment of the presentinvention;

FIG. 7 is a first sequence chart showing, in a communication systemaccording to a communication system according to an embodiment of thepresent invention, in a case in which an MN makes a request to a proxyfor a preparation of establishment of a QoS path, one example of anoperation to be conducted at the preparation;

FIG. 8 is a second sequence chart showing, in a communication systemaccording to a communication system according to an embodiment of thepresent invention, in a case in which an MN makes a request to a proxyfor a preparation of establishment of a QoS path, one example of anoperation to be conducted at the preparation;

FIG. 9 is an illustrative view showing a configuration of a radiocommunication system common to the present invention and a conventionaltechnique;

FIG. 10 is an illustrative view for explaining the fact that an RSVPaccording to a conventional technique cannot cope with the movement ofan MN;

FIG. 11 is an illustrative view for explaining a protocol arrangement ofan NSIS according to a conventional technique;

FIG. 12 is an illustrative view for explaining the concept of “adjacent”of an NE or QNE which is a node of an NSIS according to a conventionaltechnique;

FIG. 13 is an illustrative view showing a method of carrying out a QoSresource reservation in an NSIS according to a conventional technique;

FIG. 14 is an illustrative view for explaining a method of avoiding adouble resource reservation in an NSIS according to a conventionaltechnique;

FIG. 15 is an illustrative view showing one example of proxy informationto be stored in an MN according to an embodiment of the presentinvention;

FIG. 16 is an illustrative view showing one example of AP-ARcorrespondence information to be stored in an MN according to anembodiment of the present invention;

FIG. 17 is a sequence chart showing, in a communication system accordingto an embodiment of the present invention, one example of an operationin a case in which an MN makes a request to a proxy for a preparation ofestablishment of a QoS path and an RESPONSE message used in aconventional NSIS is used as a message for use in the preparation;

FIG. 18 is a sequence chart showing, in a communication system accordingto an embodiment of the present invention, one example of an operationin a case in which an MN makes a request to a proxy for a preparation ofestablishment of a QoS path and an RESPONSE message used in aconventional NSIS is used as a message for use in the preparation;

FIG. 19 is a block diagram showing a configuration of a proxy forrealizing a different processing method after the reception of a messageC according to an embodiment of the present invention;

FIG. 20 is a block diagram showing a configuration of an CN forrealizing a different processing method after the reception of a messageB according to an embodiment of the present invention;

FIG. 21 is a sequence chart showing, in a communication system accordingto an embodiment of the present invention, one example of an operationto be conducted in a case in which a proxy makes a request to a CRN forthe establishment of a QoS path;

FIG. 22 is a first sequence chart showing, in a communication systemaccording to an embodiment of the present invention, in a case in whichan MN makes a request to a proxy for a preparation of establishment of aQoS path, one example of an operation to be conducted at thepreparation;

FIG. 23 is a second sequence chart showing, in a communication systemaccording to an embodiment of the present invention, in a case in whichan MN makes a request to a proxy for a preparation of establishment of aQoS path, one example of an operation to be conducted at thepreparation;

FIG. 24 is a sequence chart showing one example of an operation in acase in which an MN finds an CRN without sending a message to a CN; and

FIG. 25 is a flow chart showing, in a communication system according toan embodiment of the present invention, one example of a method ofmaking a judgment as to whether or not a QNE itself, which has receiveda message, is a CRN.

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the present invention will be described hereinbelow withreference to FIGS. 1 to 8, 15 and 16. FIG. 1 is an illustrative viewshowing a configuration of a communication system according to anembodiment of the present invention. In FIG. 1, a QoS path (path 24)established with respect to a CN 60 is shown by a solid line in a statewhere an MN 10 is connected to a subnet 20 before handover. On this path24, there exist an AR 21, an NE 62, a QNE 63, an NE 64, a QNE 65 and aQNE 66 in a direction from the MN 10 to the CN 60. Likewise, in a casein which the MN 10 makes a connection to a subnet 30 after the handover,a QoS path (path 34) established with respect to the CN 60 is shown by adotted line. On the path 34, there lie an AR 31, a QNE (proxy) 68, a QNE67, an NE 64, a QNE 65 and a QNE 66 in a direction from the MN 10 to theCN 60. Therefore, the QNE (CRN) at which the old path (path 24) and thenew path (path 34) intersect with each other is the QNE 65.

Secondly, a description will be given of the functions of the MN 10.FIG. 2 is a block diagram showing a configuration of an MN according toan embodiment of the present invention. In FIG. 2, although eachfunction of the MN 10 is shown in the form of a block, the respectivefunctions thereof are realizable by hardware and/or software. Inparticular, the principal processing (processing in each step shown inFIG. 7, which will be mentioned later) according to the presentinvention executable through the use of a computer program.

The MN 10 shown in FIG. 2 is made up of a handover accepting candidatedetermining means 101, a radio reception means 102, a radio transmissionmeans 103, a proxy determining means 104, a message generating means 105and a message receiving means 106. In addition, as options, it is alsoappropriate that it includes an NCoA configuring means 107 and a proxyinformation storing means 108. In FIG. 2, the option sections are shownby dotted lines.

The handover accepting candidate determining means 101 is, for example,a means to receive signals from a plurality of APs different from eachother to seek a list of L2-handover-acceptable APs. In this connection,it is also possible that the MN 10 directly conducts the processing inthe proxy determining means 104, mentioned later, without determining anL2 handover accepting candidate in the handover accepting candidatedetermining means 101. Moreover, each of the radio reception means 102and the radio transmission means 103 is a means to data reception ordata transmission through radio communication, and has various functionsneeded for the radio communication.

The proxy determining means 104 is for finding a proxy. The proxy to befound by the proxy determining means 104 signifies an NSIS node (QNE)with a QoS offering function, capable of making a preparation as anagent of the MN 10 in advance so that the MN 10 can continuously acceptan additional service (in this case, QoS) after the handover, and existson a QoS path scheduled to be set up when the MN 10 implements thehandover.

A plurality of methods are considered for finding this proxy. Forexample, there are a method of referring to proxy information 40 (proxyinformation 40 stored in the proxy information storing means 108) keptlocally in the MN 10 on the basis of the information on an AP listacquired by the handover accepting candidate determining means 101 so asto retrieve and determine the proxy information 40 suitable for thecommunication with the CN 60 on a subnetwork to which the AP is inconnection, a method of transmitting this AP list information to aserver (proxy retrieving server) lying on an IP network, or the like, toreceive the information related to the most suitable proxy, mentionedabove, as a response, a method of selecting all the proxies kept in theproxy information 40, and other methods. The AR itself which is ahandover accepting candidate is a QNE and sometimes becomes a proxy.FIG. 15 is an illustration of one example of contents of the proxyinformation 40. The proxy information 40 shown in FIG. 15 is one exampleproduced by referring to the network configuration shown in FIG. 9. Theproxy information 40 shown in FIG. 15 has an IP address which canselected as a proxy in a case in which an MN is in connection with eachAP, and the MN can carries out the proxy selection and identification byseeing this proxy information 40. In this connection, it is desirablethat, as a proxy, a QNE existing in the vicinity of an AR (near an AR inthe network configuration) having each AP as a following.

The message generating means 105 is for generating a message includinginformation needed for making a preparation in advance so that the MN 10can accept the QoS without interruption after the handover. As theinformation needed for making the preparation in advance so that the MN10 can accept the QoS without interruption after the handover, forexample, there are a flow identifier and a session identifier currentlyin use, a data flowing direction (direction from the MN 10 to the CN 60,direction from the CN 60 to the MN 10, or bidirectional communication),and others. The aforesaid message generated by the message generatingmeans 105 is taken as a message A.

The message receiving means 106 is for, when the proxy carries out theabove-mentioned preparation, receiving a message (referred to as amessage D) including the information, indicative of whether or not thepreparation reaches success, from the proxy, and it is omissibledepending upon a method of setting up a new QoS path. Incidentally,information obtained when the proxy has conducted the aforesaidpreparation, and others, can also be included in the message D.

In addition, the MN 10 can also specify a movement destination andgenerate an NCoA to be used at the destination to send it to the proxyof the destination. The means to generate this NCoA is the NCoAconfiguring means 107, and the generated NCoA, together with flowidentifiers and others, is stored in the message A by the messagegenerating means 105. As the NCoA generating method, conceivably, forexample, the MN 10 locally has AP-AR correspondence information 41 asshown in FIG. 16 (one example, produced with reference to FIG. 9 as wellas FIG. 15) and retrieves this AP-AR correspondence information 41 onthe basis of the information on the AP obtained by the handoveraccepting candidate determining means 101 and obtains the information onan AR (for example, link layer address of the AR, network prefix andprefix length of a subnet to which the AR pertains, or the like)connected to the AP, thereby automatically generating an NCoA in astateless fashion.

However, in this case, since the NCoA is automatically generated in astateless fashion, there is a need for a means to confirm whether or notthis NCoA is usable in the handover-accepting subnet. For this reason,there is a need to conduct the processing to select a subnet, in whichthe AR itself can become a proxy, as the handover-accepting subnet andsend a message containing an NCoA to this AR for making this AR with theproxy function examine the validity of the NCoA, or conduct the otherprocessing. Moreover, as another NCoA acquisition method, the AR (ARpertaining to the subnet 20 before the handover) currently incommunication previously receives a portion of the usable CoAs from aDHCP server of a subnet in the neighborhood and, before the MN 10 movesto a different AR (AR pertaining to the subnet 30 after the handover),allocates one of the CoAs, obtained from the DHCP server of that subnet,to the MN 10. In this case, since the CoA is allocated in a statefulfashion, there is no need to check the validity on the CoA and there isno need to impose limitation on the selection of an AR with a proxyfunction. Moreover, information (for example, information such as an IPaddress of a currently adjacent QNE (QNE 63) relative to the MN 10)other than this can also be included in the message A.

Furthermore, a description will be given of a function of a proxy (QNE68) which receives a message from the MN 10. In this case, let it beassumed that a QNE 68 in FIG. 1 is selected as one of proxies. FIG. 3 isa block diagram showing a configuration of a proxy according to anembodiment of the present invention. As well as the MN 10 shown in FIG.2, each function of the proxy 68 shown in FIG. 3 is realizable withhardware and/or software. In particular, the principal processing(processing in each step shown in FIG. 7, mentioned later) in thepresent invention is executable by a computer program.

The proxy 68 shown in FIG. 3 is made up of a reception means 681, atransmission means 682, message processing means 683, 684 and messagegenerating means 685, 686. Moreover, as options, it can also include amessage generating means 687 and a path information storing means 688.In FIG. 3, the option portions are indicated by dotted lines.

The reception means 681 and the transmission means 682 are for carryingout data reception and data transmission. The message processing means683 is for receiving and processing a message (message A) generated bythe message generating means 105 of the MN 10 shown in FIG. 2 andtransmitted by the radio transmission means 103. For example, itconfirms the information on a flow of data included in the message A andmakes a judgment on a desirable mode for the establishment of a QoSpath. A variation of the QoS path establishing method based on a flow ofdata will be described together with a function of an intermediate QNEwhich will be mentioned later.

The message generating means 685 generates a message (referred to as amessage B) including a flow identifier (for example, flow identifier Xof the path 24) and a session identifier (for example, sessionidentifier Y common to the path 24 and the path 34) which are receivedby the message processing means 683. The aforesaid message B generatedby the message generating means 685 is a message for finding an CRN andis transmitted through the transmission means 682 toward the CN 60.Incidentally, IP address information on the CN 60 is included in thisflow identifier.

The message processing means 684 is for receiving and processing amessage (referred to as a message C) sent, through each QNE on the path34, from the CN 60 which has received the message B generated by themessage generating means 685 and transmitted. This message C includesthe information on the CRN. On the basis of this CRN information, themessage processing means 684 conducts the processing to promptlyestablish a QoS path at the handover of the MN 10. Conceivably, thereare a plurality of methods of carrying out this processing. For example,it is also appropriate that this information is handed over to the pathinformation storing means 688 and some processing is conducted when theMN 10 tries to conduct the handover, or that the information is furtherhanded over to the message generating means 686 and is used as are turnmessage (the above-mentioned message D) to the MN 10. However, this caserequires that the message receiving means 106 shown in FIG. 2 isprovided in the MN 10. Moreover, it is also appropriate that, asmentioned above, the message D includes the information indicative ofwhether or not the preparation reaches success. Still moreover, themessage D can also include information other than this information.

In addition, it is also appropriate that, in a case in which the messageprocessing means 683 receives the information on the NCoA of the MN 10,the message generating means 687 generates a new flow identifier on thebasis of this NCoA and transmits an RESERVE message to the CN 60 on thebasis of the CRN information received by the message processing means684 so as to generate a new QoS path on the path 34. However, in thiscase, there is a need to provide, for example, a different functionwhereby the CRN information is given to the RESERVE message and thecorresponding CRN prevents a double reservation of a resourcereservation from it up to the CN 60. For example, by referring to theinformation on a CRN included in the message C, the information on aQSpec needed for the establishment of a QoS path and included in theRESERVE message, and other information, can be acquired from this CRN.Still additionally, in a case in which the information on the currentlyadjacent QNE (QNE 63) relative to the MN 10 is included in the messageA, it is also possible to acquire them from the QNE 63. Yetadditionally, in a case in which there is a need to check the validityof the NCoA sent as mentioned above, this check becomes necessary. Ifthis proxy does not have a function to check the validity of the NCoA,or when the result of the validity check indicates no appropriateness,for example, a need exists for returning an error message for errornotification to the MN 10. This error notification can be included inthe message D, or it can also be returned as a different message (forexample, FBAck message in FMIP). Moreover, the information (for example,information such as an NCoA on which the validity is confirmed and thecurrently adjacent QNE (QNE 63) of the MN 10 included in the message A)other than mentioned above can be included in the message B generated inthe message generating means 685.

Secondly, taking note of the QNE 65 as an example, a description will begiven of a function of an intermediate QNE on the path 34. FIG. 4 is ablock diagram showing a configuration of an intermediate QNE on the path34 according to an embodiment of the present invention. In the case ofthe MN 10 shown in FIG. 2, each function of the QNE 65 shown in FIG. 4is realizable with hardware and/or software. In particular, theprincipal processing (processing in each step shown in FIG. 7, mentionedlater) according to the present invention is executable with a computerprogram.

The QNE 65 shown in FIG. 4 is composed of a reception means 651, atransmission means 652, a message processing means 653, and a messagegenerating means 654. The reception means 651 and the transmission means652 have the same functions as those of the reception means 681 and thetransmission means 682 in the proxy 68 shown in FIG. 3. Moreover, themessage processing means 653 is for checking whether or not a resourcereservation is already present in the QNE 65 with respect to a set offlow identifier and session identifier included in the above-mentionedmessage B or message C received. If there is no reservation, nothing isdone in the message generating means 654, and the message B or themessage C is transferred to the next QNE. On the other hand, if areservation exists, in the message generating means 654, the IP addressof the interface is stored in the same message and a new messagegenerated by the message generating means 654 is transmitted through thetransmission means 652 to the next QNE. However, in a case in which themessage B or the message C makes a request to the QNE to some processingdifferent there from, for example, in the case of an extension of aQUERY message or a RESPONSE message thereto, the processing peculiar tothese message takes place.

The determination as to which of the message B and the message Cconducts the above-mentioned processing depends upon the direction offlow of data and the functions of the other NSISs. As one example, in acase in which the data flow is in a direction from the CN 60 to the MN10, from the way of thinking based on a QoS path establishing methodaccording to the RSVP (see Non-Patent Document 3), it is appropriatethat the above-mentioned processing is conducted upon receipt of themessage C sent from the CN 60.

Since it is considered that the path through which data or signalingpasses varies between a direction (referred to as upstream) from the MN10 to the CN 60 and a direction (referred to as downstream) from the CN60 to the MN 10, as a practical problem, it is considered that themessage C passes through the path 34 (can establish the path 34) whereas the message B does not pass the path 34. Accordingly, there is apossibility that each QNE on the path 34 receives only one of themessage B and the message C.

Conversely, in a case in which the same way of thinking is taken, whenthe data flow is an upstream, the path 34 is established by the messageB and the processing is conducted by the aforesaid message processingmeans 653 and message generating means 654. In this case, the message Ccan serve as a message for only returning, to the proxy 68, a result ofthe processing conducted by each QNE at the reception of the message B.However, in the NSIS, due to the utilization of the function of theNTLP, the way of thinking of the path establishing method according tothe RSVP does not always apply thereto. For example, in the case of thedata flow in the downstream direction, the message B passes through thepath 34, and the necessary information is collectable.

Furthermore, a description will be given of a function of the CN 60.FIG. 5 is a block diagram showing a configuration of a CN according toan embodiment of the present invention. As in the case of the MN 10shown in FIG. 2, each function of the CN 60 shown in FIG. 5 isrealizable with hardware and/or software. In particular, the principalprocessing (processing in each step shown in FIG. 7, mentioned later)according to the present invention is executable through the use of acomputer program.

The CN 60 shown in FIG. 5 includes a reception means 601, a transmissionmeans 602, a message processing means 603, a message generating means604 and a path information storing means 605. The reception means 601and the transmission means 602 have the same functions as those of thereception means 681 and the transmission means 682 in the proxy 68 shownin FIG. 3 and the reception means 651 and the transmission means 652shown in FIG. 4. Moreover, the message processing means 603 has afunction to receive and process the message B. For example, the messageprocessing means 603 makes a decision as to whether the message B isissued with respect to the upstream or with respect to the downstream.Still moreover, when the message B includes information on a CRN for theupstream, the message processing means 603 can also hand over thisinformation on the CRN to the path information storing means 605 so thatthe path information storing means 605 holds it. When obtaining theinformation on the NCoA of the MN 10 by using the information stored inthe path information storing means 605, the CN 60 can conduct the QoSpath establishment processing using the RESERVE message. The informationon the NCoA of the MN 10 can be acquired simultaneously with thereception of the message B when it is included in the message B, and canalso be acquired through a BU message from the MN 10. Yet moreover, theinformation on QSpec included in the RESERVE message and others canobtained from the CRN as mentioned above and, if the message B includesthe IP address of the QNE 63, it can also be obtained from the QNE 63.In addition, the message generating means 604 is a means for generatingthe message C and transmitting the message C through the transmissionmeans 602. In this connection, if the path information (information onwhich of QNEs has kept the resource reservation) is included in themessage B, it is also possible to put it in the message C before thetransmission. The message C can also include information other than theabove-mentioned information.

Furthermore, a description will be given of an approach for the CN 60 orthe proxy 68 to acquire the information on the CRN through thetransmission/reception of the message B and the message C. Now, let itbe assumed that the MN 10 and the CN 60 are in bidirectionalcommunication with each other through the use of, for example, IPtelephony. In this case, as the data flow, there are upstream anddownstream, and these bidirectional data do not always pass through thesame path (same router), and it is considered that the CRN also variesbetween the upstream side and the downstream side. In this case,although it is assumed that the bidirectional data pass through the samepath, even in the case in which the bidirectional data pass throughdifferent paths, it is possible to determine a CRN for each of thebidirectional communications through the use of a method similar to amethod which will be mentioned later. In the case of the bidirectionalcommunications, a flow identifier and a session identifier exist withrespect to a communication path in each of the directions, and the proxymay obtain a set of flow identifier and session identifier in each ofthese two directions from the MN 10 and put them in the message beforetransmitting to the CN 60.

FIG. 6 is an illustration of one example of information which canprovide a proxy through the transmission/reception of the messages B andC. The information on an IP address of an interface having a resourcereservation is added to the end portion of each of the messages B and Cwhenever each of the messages B and C passes through a QNE having thisresource reservation with respect to a pair of flow identifier andsession identifier of each of the messages B and C. For example, in thecase of the message B, when it passes through the QNE 65, an IP address(information 81: IP address of an interface on the upper side (QNE 66side) of the QNE 65) of an interface having a resource reservationhaving upstream flow identifier and session identifier is added thereto,and when it passes through the QNE 66, an IP address (information 82: IPaddress of an interface on the upper side (CN 60 side) of the QNE 66) ofan interface having a resource reservation having upstream flowidentifier and session identifier in the interior of the QNE 66 is addedto a further rear portion thereof. Through the use of this mechanism,when this information is returned to the CN 60 or the proxy 68, the CN60 or the proxy 68 can make a judgment that the QNE having the IPaddress (IP address of the information 81) of the interface added in thefirst place is an upstream CRN. Moreover, with respect to thedownstream, the sequence becomes reversed and, hence, the proxy 68 canmake a decision that, of the information 83 and the information 84, theQNE having the IP address (IP address of the information 84) of theinterface added at last is a downstream CRN. Incidentally, the QoS pathcan vary due to a factor such as a network condition, and there is apossibility that the CRN also varies. For coping with the possibility ofsuch a variation of the CRN, a term of validity is set with respect tothe information on the CRN held by the CN 60 or the proxy 68 and, beforethe term of validity expires, the CN 60 or the proxy 68 can also confirmwhether or not a variation occurs in the CRN or acquires the informationon the latest CRN so as to hold accurate information on the CRN.Incidentally, the CN 60 or the proxy 68 which receives the informationon the CRN can also perform this setting of the term of validity, or theterm of validity can also be notified to the CN 60 or the proxy 68 whenthe MN 10 sends the message A.

Furthermore, a description will be given of an operation to be conductedin a case in which the MN 10 makes a request to the proxy 68 for thepreparation of establishment of a QoS path and the preparation takesplace. FIGS. 7 and 8 are sequence charts showing an example of anoperation to be conducted according to the embodiment of the presentinvention when the MN 10 sends information on identifiers (flowidentifier and session identifier) to the proxy 68 and the proxy 68 andthe CN 60 interchange messages through intermediate QNEs 65 to 67 forfinding an upstream or downstream CRN. The sequence charts shown inFIGS. 7 and 8 apply to a case in which, in the network system shown inFIG. 1, the MN 10 selects the proxy 68 as one of proxies and, in thiscase, after acquiring the information on the CRN, the proxy 68 is madeto return this information to the MN 10. Moreover, the sequence chartsshown in FIGS. 7 and 8 indicate a series of operations and a step S523shown in he sequence charts of FIGs. 7 and 8 conducts the sameprocessing.

Upon receipt of L2 information from an L2 signal reachable AP in theneighborhood, the MN 10 first determines a handover-acceptablesubnetwork on the basis of this information (step S501: determining ahandover-accepting candidate) and then determines a proxy for thehandover-accepting candidate on the basis of the L2 information of theAP (step S503: determining the QNE 68 as one of proxies (proxy 68)). TheMN 10 which has determined the proxy sets upstream flow identifier andsession identifier and downstream flow identifier and session identifieron the path 24 in the message A and further sets information indicativeof bidirectional communication therein (step S505: setting upstream anddownstream flow identifiers and session identifiers on the path 24 and“bidirectional communication” in the message A), and transmits themessage A to the selected proxy group (a plurality of proxies) (stepS507). In this case, in particular, a description will be limited to theprocessing to be conducted after the message A is sent to the proxy 68which is one of the proxy group. Incidentally, the message A can includeinformation (IP address or the like) on the destination of the messageB. Although the destination of the message B is the CN 60 in FIGS. 7 and8, for example, in a case in which a retrieval of a CRN on a QoS path ismade with respect to a communication using a triangular path in themobile IP6, it is also acceptable that the destination of the message Bis set at a home agent of the MN 10.

The proxy 68 generates a message B on the basis of the information onthe message A received from the MN 10. Since the bidirectionalcommunication is considered in this case, a parameter is set so that, ina router lying on the way, the upstream information is obtainablethrough the message B and the downstream information is obtainablethrough a reply message (message C), and a flow identifier and a sessionidentifier, sent through the message A, are set in the message B (stepS509: setting a parameter in the message B so that the upstreaminformation is attainable through the message B and the downstreaminformation is attainable through the message C, and additionallysetting the received flow identifier and session identifier in themessage B), and the message B is sent to the CN 60 (step S511).Incidentally, at this time, there is a need for the proxy 68 to acquirethe address of the CN 60.

Each of the QNEs 65 to 67 on a path from the proxy 68 to the CN 60confirms the contents of the message B so as to confirm whether or not aresource reservation relative to the upstream flow identifier andsession identifier there in exists in the QNE. If the resourcereservation relative to the upstream flow identifier and sessionidentifier exists, each QNE adds the IP address of the interface havingthis resource reservation to the message B and sends it toward the CN60. On the other hand, if the resource reservation relative to theupstream flow identifier and session identifier does not exist, each QNEtransfers the message B as it is without adding the information.

In this connection, since the resource reservation relative to theupstream flow identifier and session identifier does not exist in theQNE 67, the message B is directly transferred without the addition ofthe information (step S513: sending the message B to the next in a stateuntouched because of no existence of the resource reservation relativeto the upstream flow identifier and session identifier, step S515)Moreover, since the resource reservation relative to the upstream flowidentifier and session identifier exists in the QNE 65, the IP addressof the interface having this resource reservation is added to themessage B and the message B is then transferred (step S517: setting theIP address of the interface having the resource reservationcorresponding to the received upstream flow identifier and sessionidentifier, step S519). Moreover, as well as the QNE 65, since theresource reservation relative to the upstream flow identifier andsession identifier exists in the QNE 65, the IP address of the interfacehaving this resource reservation is added to the message B and themessage B is then transferred (step S521: setting the IP address of theinterface having the resource reservation corresponding to the receivedupstream flow identifier and session identifier, step S523).

Lastly, the message B arrives at the CN 60 and, upon receipt of thismessage B, the CN 60 sets, in the message C, the information(information added to the message B by the respective QNEs 65 to 67)added by the respective QNEs 65 to 67, and sets a parameter so as tocollect the information on the downstream path through the message C(step S525: setting the contents of the message B in the message C andsetting a parameter for collecting the downstream information throughthe message C) and transmits it to the proxy 68 (step S527. Moreover,each of the QNEs 65 to 67 lying on the path from the CN 60 to the proxy68 carries out the processing, similar to the processing on theabove-mentioned message B, with respect to the message C.

Since a resource reservation corresponding to the downstream flowidentifier and session identifier exists in the QNE 66, the IP addressof the interface having this resource reservation is added to themessage B and the message B is then transferred (step S529: setting theIP address of the interface having a resource reservation correspondingto the received downstream flow identifier and session identifier, stepS531). Moreover, as well as the QNE 65, a resource reservationcorresponding to the downstream flow identifier and session identifierexists in the QNE 65, the IP address of the interface having thisresource reservation is added to the message B and the message B is thentransferred (step S533: setting the IP address of the interface having aresource reservation corresponding to the received downstream flowidentifier and session identifier, step S535). Still moreover, since aresource reservation corresponding to the downstream flow identifier andsession identifier does not exist in the QNE 67, the message B istransferred in an intact condition without adding the information (stepS537: transmitting it to the next as it stands because of no resourcereservation corresponding to the received downstream flow identifier andsession identifier, step S539).

The proxy 68, which receives the message C in this way, can specify theCRN information for the upstream and the downstream by referring to themessage C, and sets the CRN information for the upstream and thedownstream in a message D (step S541: setting the CRN information forthe upstream and the downstream in a message D) and transmits themessage D to the MN 10 (step S543).

As mentioned above about the function of the MN 10, after the collectionof the information on the CRN, in addition to sending the CRNinformation to the MN 10, the proxy 68 can take various measures.Moreover, when learning the CRN information at an early stage, forexample, the MN 10 can put this CRN information in a RESERVE message inthe case of making a resource reservation after the movement from thesubnet. Still moreover, when the relevant CRN receives the RESERVEmessage including the CRN information, the relevant CRN can conduct theprocessing so as to prevent the double reservation of resources up tothe succeeding CN 60. For example, the relevant CRN can also conduct theprocessing such as updating the old reservation without newly making areservation of a resource.

In a case in which the CRN is specified in advance in this way, even ifit is a resource reservation after the handover of the MN 10, since theresource reservation is not made while seeking a CRN unlike theconventional technique, the setup of a QoS path becomes promptlyfeasible. Moreover, as mentioned above, the proxy 68, which has obtainedthe CRN information, can also make a resource reservation in advancewithout returning the information to the MN 10, which realizing theestablishment of a QoS path more promptly.

In addition, as mentioned above, it is also possible to rewrite themessage B or the message C into the existing message, for example, theQUERY message, the RESPONSE message or the NOTIFY message. FIGS. 17 and18 show a sequence chart in a case in which the QUERY message has thefunction of the message B and the RESPONSE message has the function ofthe message C. In this case, a message to be interchanged has not only afunction to find upstream and downstream CRNs but also the intendedfunctions (function for acquiring information on a free resource, andother functions) of the QUERY and RESPONSE messages. In FIGS. 17 and 18,steps S551 to S593 are in correspondence relation to the steps S501 toS543 in FIGS. 7 and 8, and the QUERY message and the RESPONSE messageare in correspondence relation to the message C and the message D,respectively.

As mentioned above, in the case of employing the conventional QUERY andRESPONSE messages, since a terminal such as the MN 10, which is made tomove, does not have a means to seize the information on a resourcereserved through the present communication with a communication partner,difficulty is experienced in making a decision that the information onthe resource reserved through the present communication between the CRNand the CN 60 is the information on a resource available at the movementof the MN 10 thereto. However, when the QUERY and RESPONSE messages havethe information on the present flow identifier and session identifier ofthe MN 10, a decision can be made that the information on the resourcereserved through the present communication is the information on aresource available at the movement of the MN 10 thereto.

In this connection, according to the Non-Patent Document 6, theinformation on the free resource is obtainable by only the RESPONSEmessage. That is, as shown in FIGS. 17 and 18, when the proxy 68transmits a QUERY message to the CN 60 and the CN 60 returns a RESPONSEmessage, there is a possibility that only the information on thedownstream resource is attainable. Accordingly, when the bidirectionalfree resource information is necessary, it is considered that there is aneed for the CN 60 which has received the QUERY message from the proxy68 to return the RESPONSE message to the MN 10 and to transmit adifferent QUERY message to the proxy 68 at the same time. Moreover,there is a possibility that, through the use of a combination with adifferent function of the NSIS, the bidirectional free resourceinformation is attainable through single transmission/reception of theQUERY and RESPONSE messages.

Incidentally, as the method in which the proxy 68 processes the CRNinformation (CRN information included in the message C) obtained by themessage processing means 684 shown in FIG. 3 and the method in which theCN 60 processes the CRN information (CRN information included in themessage B) obtained by the message processing means 603 shown in FIG. 5,other methods are also conceivable. These methods will be described withreference to FIGS. 19 and 20.

FIG. 19 is a block diagram showing a configuration of a proxy forrealizing a processing method after the reception of a message Caccording to an embodiment of the present invention. As well as theproxy 68 shown in FIG. 3, each function of the proxy 68 shown in FIG. 19is realizable with hardware and/or software. Moreover, a reception means6811, a transmission means 6812, message processing means 6813, 6814,message generating means 6815, 6816, 6817 and a path information storingmeans 6818 in FIG. 19 have the same functions as those of the receptionmeans 681, the transmission means 682, the message processing means 683,684, the message generating means 685, 686, 687 and the path informationstoring means 688, respectively, and the description thereof will beomitted here.

The message generating means 6819 shown in FIG. 19 has a function togenerate a message (referred to as a message E) for making a request toa different node for the generation of a QoS path and to hand over it tothe transmission means 6812. For example, a CRN specified through theprocessing related to the message B in the message processing means 6814is considered as the destination of the message E. In this case, themessage E includes the information (for example, the NCoA of the MN 10whose validity has been confirmed, the IP address of the CN 60, or thelike) needed for the generation of a QoS path by the CRN. The CRN whichhas received the message E from the proxy 68 transmits a RESERVE messageto, for example, both the CN 60 and the proxy 68, thereby updating theQoS path from the CRN to the CN 60 for newly generating a QoS path fromthe CRN to the proxy 68.

FIG. 20 is a block diagram showing a configuration of a CN for realizinga different processing method after the reception of a message Baccording to an embodiment of the present invention. As well as the CN60 shown in FIG. 5, each function of the CN 60 shown in FIG. 20 isrealizable with hardware and/or software. Moreover, a reception means6011, a transmission means 6012, a message processing means 6013, amessage generating means 6014 and a path information storing means 6015in FIG. 20 have the same functions as those of the reception means 601,the transmission means 602, the message processing means 603, themessage generating means 604 and the path information storing means 605in FIG. 5, respectively, and the description thereof will be omittedhere.

The message generating means 6016 shown in FIG. 20 has a function togenerate a message (referred to as a message E) for making a request toa different node for the generation of a QoS path and to hand it over tothe transmission means 6012. For example, a CRN specified through theprocessing related to the message B in the message processing means 6013is considered as the destination of the message E. In this case, themessage E includes the information (for example, the NCoA of the MN 10whose validity has been confirmed and which has been obtained throughthe method mentioned above, the IP address of the proxy 68 which is asource of the message B, or the like) needed for the generation of a QoSpath by the CRN. The CRN which has received the message E transmits aRESERVE message to, for example, both the CN 60 and the proxy 68,thereby updating the QoS path from the CRN to the CN 60 for newlygenerating a QoS path from the CRN to the proxy 68.

Secondly, a description will be given of an operation in which the proxy68 makes a request for the generation of a QoS path to the CRN specifiedthrough the reception of the message C. In this case, although it isassumed that bidirectional communications are taken and thebidirectional paths are equal to each other, even in a case in whichonly one of the upstream side and the downstream side is taken or thebidirectional data communication is conducted and the bidirectionalpaths are different between the upstream side and the downstream side,when methods similar to methods which will be mentioned later are usedseparately for the upstream path or bidirectional paths, theimplementation of the QoS path generation request is feasible.

FIG. 21 is an illustration of a sequence chart showing an example of anoperation in which the proxy 68 which has received a message (message A)including an NCoA from the MN 10 makes a request for a production of anew QoS path to a downstream CRN specified through the interchange ofmessages (message B and message C) with respect to the CN 60. Thesequence chart shown in FIG. 21 signifies a case in which, in thenetwork system shown in FIG. 1, the proxy 68 is selected as one of theproxies by the MN 10. Moreover, although the processing similar to thoseof the steps S511 to S523 in FIG. 7 and the steps S525 to S529 in FIG. 8are conducted between steps S5005 and S5007 in FIG. 21, they are omittedhere.

The proxy 68 generates a message B on the basis of the information onthe message A received from the MN 10. Since the bidirectionalcommunication is considered in this case, the proxy 68 sets a parameterso that, through a router on the way, the upstream information isobtainable by the message B and the downstream information is attainableby a reply message (message C), and further sets a flow identifier and asession identifier, sent through the message A, in the message B (stepS5001: receiving the message A, and making the preparation for thetransmission of the message B) to transmit the message B to the CN 60(step S5005: transmitting the message B toward the CN 60). In thisconnection, at this time, the proxy 68 is required to obtain the addressof the CN 60 through the use of the flow identifier information.Moreover, the proxy 68 makes a preparation for the transmission of themessage B in the step S5001 and further checks the validity of the NCoAof the MN 10 included in the message A (step S5003: checking thevalidity of the NCoA of the MN 10 included in the message A). Inaddition, upon receipt of the message C which is a reply message to themessage B transmitted in the step S5005, the proxy 68 refers to themessage C so as to specify the information on the CRNs for the upstreamand the downstream (step S5007: receiving the message C, and obtainingthe information on the CRN (QNE 65) for the upstream and thedownstream). The proxy 68 sets, in the message E, the information neededwhen these CRNs establish a new QoS path (step S5009: setting, in themessage E, the information needed for the CRNs (QNE 65) to generate anew QoS path), and transmits the message E to each of the CRNs for theupstream and the downstream obtained in the step S5007 (Steps S5011 andS5013). In this case, although the both the CRNs for the upstream andthe downstream becomes the QNE 65, since it is considerable that theinterface addresses of the CRNs for the upstream and the downstreamdiffer from each other (different interface addresses in the QNE 65 areacquired as the CRNs for the upstream and the downstream in the stepS5007), the message E is transmitted separately to the upstream anddownstream sides. For example, a flow identifier to be used in a new QoSpath, or the like, is considered as the information needed when the CRNsestablish a new QoA path. This new flow identifier can be generated onthe basis of the NCoA of the MN 10 confirmed in validity in the stepS5003. Moreover, conceivably, the IP address of the CN 60, a sessionidentifier, or the like, are considered as the information needed whenthe CRNs establish a new QoA path.

Upon receipt of the message E, the QNE 65 transmits a RESERVE message,for updating the QoS path, to the CN 60 (step S5015), and transmits aRESERVE message, for newly generating a QoS path, to the proxy 68 (step5017). In this case, both the QoS paths for the upstream and thedownstream are updated in the step S5015, and both the QoS paths for theupstream and the downstream are newly generated in the step S5017.

In addition, also in a case in which a request is made to the upstreamCRN for the generation of a new QoS path after the CN 60 acquires theinformation on the upstream CRN, a similar method is employable. In thiscase, after acquiring the upstream CRN information and the NCoA of theMN 10 having validity, the CN 60 shown in FIG. 20 transmits the messageE to the upstream CRN. Incidentally, in this case, it is also possiblethat the information on the IP address of the proxy 68 is included inthe message E.

Still additionally, through the proxy determining means 104 of the MN 10shown in FIG. 2, the MN 10 can also select the CN 60 as a proxy. Yetadditionally, the CN 60 can also have not only a function similar tothat of the proxy 68 shown in FIG. 3 but also the function of the CN 60shown in FIG. 5, and the proxy 68 can also have, in addition to afunction similar to that of the CN 60 shown in FIG. 5, the function ofthe proxy 68 shown in FIG. 3. In this case, the CN 60 which has receivedthe message A from the MN 10 can transmit/receive the message B and themessage C with respect to the proxy 68, thereby obtaining theinformation on the CRN.

Referring to sequence charts of FIGS. 22 and 23, a description will begiven of an operation in a case in which the CN 60 is selected as theproxy 68 as mentioned above. The sequence charts shown in FIGS. 22 and23 show a series of operations, and the steps S5043 shown in thesequence charts of FIGS. 22 and 23 carry out the same processing.Moreover, the sequence charts shown in FIGS. 22 and 23 shows a case inwhich, in the network system shown in FIG. 1, the subnet 30 is selectedas a candidate for a subnetwork of a movement destination of the MN 10and, after obtaining the information on the CRN, the CN 60 returns thisinformation to the MN 10.

In FIG. 22, when receiving the L2 information from an L2-signalreachable AP in the neighborhood, the MN 10 first determines a handoveracceptable subnetwork on the basis of this information (step S5021:determining a handover accepting candidate) and then, on the basis ofthe L2 information from the AP, makes a decision on a QNE (QNE closestto the AR 31 on the path 34 in a case in which, in FIG. 1, the subnet 30is taken as a movement destination) adjacent to the MN 10 on a QoS path,established when the MN 10 moves to the subnetwork, (step S5023: makinga decision that the QNE 68 is a QNE closest to the AR 31 on the path34). For this decision, a method similar to the method in theabove-described embodiment, which is conducted when the MN 10 determinesa proxy, is employable.

The MN 10 sets, in the message A, the information on the QNE (QNE 68)decided in the step S5023 (step: S5025: setting the information on theQNE 68 in the message A). In particular, a description will be givenherein of a case in which the information on the QNE 68 is set in themessage A as one of the information on the QNE information which hasundergone the decision in the step S5023. Incidentally, upstream flowidentifier and session identifier on the path 24, downstream flowidentifier and session identifier thereon, and the informationindicative of bidirectional communication can also be set in the messageA. Following this, the MN 10 transmits this message A to the CN 60 (stepS5027).

The CN 60 generates a message B on the basis of the information on themessage A received from the MN 10. Since the bidirectional communicationis considered in this case, the CN 60 sets a parameter so that, from arouter on the way, the downstream information is obtainable with themessage B and the upstream information is obtainable with the replymessage (message C), and sets a flow identifier and a session identifierin the message B (step S5029: setting a parameter in the message B sothat the downstream information is attainable through the message B andthe upstream information is attainable through the message C, andadditionally setting the flow identifier and the session identifier inthe message B) and transmits the message B to the QNE 66 (step S5031).Incidentally, if the information on the flow identifier and sessionidentifier to be set in the message B are included in the message B, itis also possible to copy these information included in the message Ainto the message B. On the other hand, also in a case in which theinformation on the flow identifier and the session identifier are notincluded in the message A, the CN 60 can set the information on the flowidentifier and the session identifier, which are being used in thepresent communications with respect to the MN 10, in the message B.

Each of the QNEs 65 to 67 lying on the path from the CN 60 to the QNE 68confirms the contents of the message B to confirm whether or not aresource reservation relative to the downstream flow identifier andsession identifier thereof exists in each of the QNEs 65 to 67. If theresource reservation relative to the downstream flow identifier andsession identifier exists therein, each of the QNEs 65 to 67 adds the IPaddress of the interface in which this resource reservation exists tothe message B and then sends this message B to the QNE 68. On the otherhand, if the resource reservation relative to the downstream flowidentifier and session identifier does not exist therein, the message Bis transferred in an intact condition without adding the information.

In this connection, the resource reservation relative to the downstreamflow identifier and session identifier exists in the QNE 66 and, afterthe IP address of the interface where this resource reservation existsis added to the message B, the message B is transferred (step S5033:setting the IP address of the interface having the resource reservationrelative to the received downstream flow identifier and sessionidentifier, step S5035). Moreover, as well as the QNE 66, the resourcereservation on the downstream flow identifier and session identifieralso exists in the QNE 65 and, after the IP address of the interfacehaving this resource reservation is added to the message B, the messageB is transferred (step S5037: setting the IP address of the interfacehaving the resource reservation relative to the received downstream flowidentifier and session identifier, step S5039). On the other hand, sinceno resource reservation relative to the downstream flow identifier andsession identifier exists in the QNE 67, the message B is transferred inan intact condition without adding the information (step S5041:transmitting the message B to the next as it is because of no resourcereservation relative to the received downstream flow identifier andsession identifier, step S5043).

Lastly, the message B arrives at the QNE 68, and upon receipt of thismessage B, the QNE 68 sets the information added by each of the QNEs 65to 67 (information added to the message B by each of the QNEs 65 to 67)in the message C and sets a parameter so that the information for theupstream path can be collected through the message C (step S5045:setting the contents of the message B, and setting a parameter so as tocollect the upstream information through the message C), and transmitsit toward the CN 60 (step S5047). Moreover, in each of the QNEs 65 to 67existing on the path from the QNE 68 to the CN 60, in the case ofreceiving the message C, the processing similar to the aforesaidprocessing with respect to the message B is conducted with respect tothe upstream message C.

That is, since a resource reservation relative to the upstream flowidentifier and session identifier does not exist in the QNE 67, themessage C is transferred in an intact condition without adding theinformation (step S5049: transmitting the message C as it is because ofno resource reservation relative to the received upstream flowidentifier and session identifier, step S5051). Moreover, a resourcereservation relative to the upstream flow identifier and sessionidentifier exists in the QNE 65, and after the IP address of theinterface having this resource reservation is added to the message C,the message C is transferred (step S5053: setting the IP address of theinterface having the resource reservation relative to the receivedupstream flow identifier and session identifier, step S5055).Furthermore, as well as the QNE 65, a resource reservation relative tothe upstream flow identifier and session identifier also exists in theQNE 66, and after the IP address of the interface having the resourcereservation is added to the message C, the message C is transferred(step S5057: setting the IP address of the interface having the resourcereservation relative to the received upstream flow identifier andsession identifier, step S5059).

The CN 60 which has received the message C in this way can specify theinformation on the CRN for each of the upstream and the downstream byreferring to the message C, and sets the information on the CRN for eachof the upstream and the downstream in the message D (step S5061: settingthe information on the CRN for each of the upstream and the downstreamin the message D), and transmits the message D to the MN 10 (stepS5063).

Incidentally, as mentioned above in the function of the MN 10, aftercollecting the information on the CRN, the CN 60 can take variousmeasures besides sending the information on the CRN to the MN 10.Moreover, although in this case it is assumed that the data is handledby the bidirectional communications and the bidirectional data passthrough the same path, also in a case in which the bidirectional datapasses through different paths, a CRN for each of the bidirectionalcommunications can be determined by employing a method similar to theabove-mentioned method.

The expression “destination” described in this embodiment, for example,the expression “transmit to the CN 60”, does not always signifydesignating and transmitting the address of the CN 60 to the IP headerdestination address but signifying that the partner which finallyreceives a message is the CN 60.

Moreover, when the data flow is the upstream, it is possible to find aCRN without sending a message up to the CN 60. Such an example will bedescribed with reference to FIGS. 1, 24 and 25.

FIG. 24 is a sequence chart showing one example of an operation in acase in which, in a communication system according to an embodiment ofthe present invention, an MN finds a CRN without sending a message to aCN, and shows a method of using a QUERY message and a RESPONSE messageas messages.

In the sequence chart shown in FIG. 24, the QNE 68 first receives atrigger for establishing a predictive path (step S2401: receiving atrigger for establishing a predictive path). This trigger is, forexample, the above-mentioned message A sent from the MN 10 to the proxy68. Moreover, this trigger includes information needed for thepreparation of establishment of a predictive path, for example, theinformation on a session identifier the MN 10 and the CN 60 use in thecurrent communication path (path 24). Since there is a possibility thata plurality of flow identifiers correspond to the session identifier,the message A can also include identification information (for example,the present flow identifier) for specifying which of flows is taken forthe preparation of establishment of a predictive path. In this case, letit be assumed that the message A includes a flow identifier used in thepath 24. Moreover, it is also appropriate that the message A includesinformation (for example, IP address of the CN 60) for specifying the CN60, and others. Still moreover, it is also appropriate that the messageA includes information (IP address or the like) on the destination ofthe message B and, for example, in a case in which a retrieval of a CRNon a QoS path is made with respect to a communication using a triangularpath in the mobile IP6, it is also possible that the destination of themessage B is set at a home agent of the MN 10 in place of the CN 60.

Upon receipt of the trigger, the proxy 68 transmits a message (forexample, QUERY message is usable) toward the CN 60 (step S2403). At thistime, it is also acceptable that, when generating a new flow identifier(flow identifier for the path 34), the proxy 68 generates a flowidentifier with its own IP address as a source address. Moreover, theQUERY message includes the information on a session identifier the MN 10and CN 60 use in the present communication path (path 24), and others.It can also include identification information (for example, the presentflow identifier) for specifying which of flows is taken for thepreparation of establishment of a predictive path.

Upon receipt of the QUERY, the QNE 67 makes a decision shown in FIG. 25.FIG. 25 is a flow chart showing one example of a method in which, in acommunication system according to an embodiment of the presentinvention, a QNE which has received the message makes a decision as towhether or not the QNE itself is a CRN. After the reception of the QUERYmessage (step S2501: receiving a message), the QNE 67 checks whether ornot the QNE 67 itself has a state (resource reservation) with respect toa session identifier included in this QUERY message (step S2502: Doesthe QNE 67 have a state relative to a session identifier included in theQUERY message?). In this case, since the QNE 67 does not have a state,the QNE 67 makes a decision as being not the CRN. Moreover, the QNE 67transmits the QUERY message toward the CN 60 (step S2405).

On the other hand, the QNE 65 which has received the QUERY message alsomakes a decision shown in FIG. 25. After the reception of the QUERYmessage (step S2501: receiving a message), the QNE 67 which has receivedthe QUERY message checks whether or not the QNE 67 itself has a state(resource reservation) with respect to a session identifier included inthis QUERY message (step S2502: Does the QNE 67 itself have a staterelative to a session identifier included in the QUERY message?). Inthis case, since the QNE 65 has this state, the QNE 65 checks whether ornot the identification information for specifying which of flows is nexttaken for the preparation of establishment of a predictive path isincluded in the QUERY message (step S2503: Is an identifier forspecifying a flow of an old path included in the QUERY message?). Inthis case, since the flow identifier used in the path 24 is included asan identifier for specifying the flow of the old path, the QNE 67subsequently checks whether or not this flow identifier is included inthe state relative to the session identifier which was checked in thestep S2501 (step S2504: a state relative to the specified flow?). In acase in which this flow identifier is not included in the state relativeto the session identifier, the QNE 67 makes a decision that it is notthe CRN, and the QUERY message is further transferred.

The QNE 65 belongs to the path 24 and a given flow identifier isincluded in the state, and the QNE 65 subsequently checks theinformation (SII: Source Identification Information) on an adjacent QNEwhich has transmitted the QUERY message thereto (step S2505: Is SIIequal?). That is, the SII information in the path 24 is included in thestate of the QNE 65 (that is, having the information indicative of theQNE 63 corresponding to SII), and the QNE 65 makes a comparison betweenthis information and the information on the QNE which has sent the QUERYmessage in the step S2405 (that is, the information on the QNE 67). Ifthe comparison decision shows that these information are different fromeach other, the QNE 65 makes a decision that the QNE 65 itself is a CRN.On the other hand, if they are identical to each other, the QNE 65 makesa decision that it is not a CRN.

When the QNE 65 makes a decision that it is a CRN (step S2407: making acomparison with a session identifier or SII so as to recognize that theQNE 65 itself is a crossover node), for notifying, to a proxy (QNE 68),the fact that it is a CRN, the QNE 65 transmits a RESPONSE message tothe proxy 68 (steps S2409 and S2411).

In addition to the QNE (in this case, the QNE 65) which has recognizedthat it is a CRN notifying, to the proxy 68, the fact that it is theCRN, various CRN using methods are conceivable. For example, in a casein which the messages sent in the step S2403 and the step S2405 includethe NCoA of the MN 10 or a flow identifier, it is also possible that theQNE 65 which has recognized that it is an CRN transmits a RESERVEmessage for setting up a new path in a direction of the MN 10 and aRESERVE message for updating in a direction of the CN 60 withoutreturning a RESPONSE message so as to conduct an operation related to aresource reservation.

Moreover, at a resource reservation, the employment of a flow identifieris not always necessary for identifying packet data to which a reservedresource is to be given. In this case, for example, a differentidentifier (in this case, referred to as a filter) can also be placed ina message (QUERY message, RESERVE message or the like). Moreover, inthis case, instead of a flow identifier, a filter can also be used as anidentifier to be used for finding a CRN or for making a resourcereservation with respect to a new path.

Incidentally, it is also appropriate that a plurality of identifierseach (flow identifier or filter) for identifying the packet data towhich a reserved resource is to be given as mentioned above exist withrespect to one resource reservation. That is, it is also acceptable thata flow identifier list or filter list exists with respect to oneresource reservation. In this case, when a QNE receives a data packethaving the information contents identical to those of one of theidentifiers existing in a list (flow identifier list or filter list),the QNE can allocate a reserved resource.

Moreover, for example, in a case of updating a reservation in a rangefrom the CRN (QNE 65) to the CN 60 as mentioned above, the concept ofthis list (flow identifier list or filter list) is also available. Oneexample will be described with reference to FIGS. 1 and 21. In thiscase, as an identifier for identifying packet data to which a reservedresource is to be given, a flow identifier is put to use, and a flowidentifier list is used as a list.

A resource reservation in an old path (path 24) currently exists in theQNE 65 and the QNE 66. That is, in the QNE 65 and the QNE 66, a resourceis allocated with respect to an identifier (or a list including thisflow identifier) including the CoA of the MN 10 before movement.

After receiving a message E in the step S5013, as the RESERVE (update)processing, the QNE 65 adds a new flow identifier (including the NCoA ofthe MN 10) included in the message E to a flow identifier list to whicha resource is allocated with respect to the path 24, and transmits aRESERVE (update) message toward the CN 60 (step S5015). Upon receipt ofthis RESERVE (update) message, the QNE 66 likewise adds the new flowidentifier to the flow identifier list to which the resource isallocated with respect to the path 24 and transmits a RESERVE (update)message toward the CN 60. Thus, the QNE 65 and the QNE 66 have aresource reservation with respect to both the path 24 and path 34. Withrespect to the path 24 and the path 34, a reservation is not separatelymade, but both the path 24 and path 34 share a resource, therebyavoiding the double resource reservation.

In addition, after this processing, the flow identifier for the path 24can be removed from the flow identifier lists of the QNE 65 and the QNE66 after the MN 10 moves to the subnet 30 and starts thetransmission/reception of data. As the removal method, it is alsoacceptable that a timer is provided so that the flow identifier isautomatically deleted when this timer becomes longer than apredetermined period of time, or that the flow identifier is explicitlydeleted by a deletion message.

INDUSTRIAL APPLICABILITY

A communication handover method, communication message processing methodand a program for executing these methods by the use of a computeraccording to the present invention enable a mobile terminal, whichconducts handover, to promptly and continuously accept an additionalservice, the mobile terminal has accepted before the handover, after thehandover, and they are applicable to a technical field related to thehandover of a mobile terminal which makes radio communications,particularly, applicable to a technical field related to the handover ofa mobile terminal which conducts radio communications using a mobile IP6protocol forming a next-generation internet protocol and related to aQoS assurance using the NSIS.

1. A communication handover method for a mobile terminal so arranged asto, in a communication system in which a plurality of access routerseach constituting a subnet are connected through a communication networkand at least one access point forming a unique communicable area isconnected to each of said plurality of access routers, make acommunication with said access router, to which said access point isconnected, through a radio communication with said access point in saidcommunicable area, comprising: a reception step of, when said mobileterminal makes communication switching from an access point which ispresently in communication to a different access point, receivinginformation on said different access point from said different accesspoint; an information acquiring step of, when the communicationswitching is made to said different access point, acquiring informationon a router capable of making a preparation related to an additionalservice, said mobile terminal desires, after the communication switchingon the basis of said information on said different access point receivedin said reception step, and an information transmitting step ofgenerating a message including information on said additional servicepresently in acceptance during communication and, on the basis of saidinformation on said router capable of making the preparation related tosaid additional service after the communication switching, sending saidmessage through said access point, which is presently in communication,to said router capable of making the preparation related to saidadditional service after the communication switching.
 2. Thecommunication handover method according to claim 1, comprising a storagestep in which said mobile terminal stores, in predetermined informationstoring means of said mobile terminal, correspondence informationdescribing correspondence relationship between said information on saidaccess point and said information on said router capable of making thepreparation related to said additional service after the communicationswitching.
 3. The communication handover method according to claim 2,wherein, in said information acquiring step, said information on saidrouter capable of making the preparation related to said additionalservice after the communication switching and associated with saidinformation on said different access point is acquired from saidcorrespondence information on the basis of said information on saiddifferent access point received in said reception step.
 4. Acommunication handover method for a mobile terminal so arranged as to,in a communication system in which a plurality of access routers eachconstituting a subnet are connected through a communication network andat least one access point forming a unique communicable area isconnected to each of said plurality of access routers, make acommunication with said access router, to which said access point isconnected, through a radio communication with said access point in saidcommunicable area, comprising: a reception step of, when said mobileterminal makes communication switching from an access point which ispresently in communication to a different access point, receivinginformation on said different access point from the different accesspoint; and an information transmitting step of generating a messageincluding said information on said different access point received insaid reception step and information on an additional service presentlyin acceptance during communication and, on the basis of said informationon said access point, transmitting said message through said accesspoint presently in communication to a predetermined server capable ofacquiring information on a router capable of, when the communicationswitching is made to said different access point, making a preparationrelated to said additional service, said mobile terminal desires, afterthe communication switching.
 5. A communication handover method for amobile terminal so arranged as to, in a communication system in which aplurality of access routers each constituting a subnet are connectedthrough a communication network and at least one access point forming aunique communicable area is connected to each of the plurality of accessrouters, make a communication with said access router, to which saidaccess point is connected, through a radio communication with saidaccess point in said communicable area, comprising: an informationtransmitting step of generating a message including information on anadditional service presently in acceptance during communication and,when said mobile terminal carries out communication switching from anaccess point presently in communication to a different access point,transmitting said message through said access point presently incommunication to all predetermined routers each capable of realizingsaid additional service after said communication switching and selectedby said mobile terminal.
 6. The communication handover method accordingto claim 1, comprising: a step in which said mobile terminal specifiesan access router having said different access point as a following onthe basis of said information on said different access point received insaid reception step; a step of acquiring information on said accessrouter having said different access point as a following; and an addressgenerating step of generating address information available in saidsubnet, to which said access router pertains, on the basis of saidinformation on said access router having said different access point asa following.
 7. The communication handover method according to claim 6,wherein, in said information transmitting step, said message istransmitted in a state where said address information generated in saidaddress generating step is included in said message.
 8. Thecommunication handover method according to claim 1, wherein saidadditional service is a QoS assurance.
 9. A communication handoverprogram for executing the communication handover method according toclaim 1 through the use of a computer.
 10. A communication messageprocessing method for a router provided in a communication system soarranged that a plurality of access routers each constituting a subnetare connected through a communication network and at least one accesspoint forming a unique communicable area is connected to each of saidplurality of access routers and a mobile terminal existing in saidcommunicable area makes a communication with said access router, towhich said access point is connected, through a radio communication withsaid access point, with said router being capable of making apreparation related to an additional service, said mobile terminaldesires, after communication switching when said mobile terminalswitches the communication with said access point, comprising: a firstinformation receiving step of receiving, from said mobile terminal, amessage including information on said additional service said mobileterminal presently accepts during communication; a step of generating amessage for a preparation of said additional service on the basis ofsaid information on said additional service; a terminal specifying stepof specifying a partner terminal, with which said mobile terminalpresently makes a communication, on the basis of said information onsaid additional service said mobile terminal presently accepts duringthe communication; an information transmitting step of generating amessage for acquiring information, which enables the preparation relatedto said additional service after the communication switching, on thebasis of said information on said additional service said mobileterminal presently accepts during the communication, and transmittingsaid message to said partner terminal; and a second informationreceiving step of receiving a message including said information, whichenables the preparation related to said additional service after thecommunication switching, from said partner terminal or from an arbitrarynode lying on a path of said message to said partner terminal.
 11. Thecommunication message processing method according to claim 10,comprising a storage step of storing said information, which enables thepreparation related to said additional service after the communicationswitching, received from said partner terminal or from said arbitrarynode lying on said path of said message to said partner terminal in saidsecond information receiving step.
 12. The communication messageprocessing method according to claim 10, comprising a step of generatinga message including said information, which enables the preparationrelated to said additional service after the communication switching,received from said partner terminal in said second information receivingstep to transmit said message to said mobile terminal.
 13. Thecommunication message processing method according to claim 12,comprising: a step of verifying the validity of said address informationwhen address information usable by said mobile terminal in said subnet,to which said access router pertains, is included in said messagereceived from said mobile terminal, which does not exist in said subnetto which said access router pertains, in said first informationreceiving step; and a step of, when the validity of said addressinformation is grasped, previously establishing a path for saidadditional service, said mobile terminal accepts after the communicationswitching, on the basis of said address information.
 14. A communicationmessage processing method for a node or a router provided in acommunication system so arranged that a plurality of access routers eachconstituting a subnet are connected through a communication network andat least one access point forming a unique communicable area isconnected to each of said plurality of access routers and a mobileterminal existing in said communicable area makes a communication withsaid access router, to which said access point is connected, through aradio communication with said access point, and made to constitute apath related to an additional service when said mobile terminal makes acommunication with a predetermined communication terminal, comprising: areservation judging step of, upon receipt of a message including a flowidentifier and a session identifier, related to a predetermined path,for checking whether said predetermined path is set or not, making ajudgment as to whether or not a resource reservation is made withrespect to said flow identifier and said session identifier included insaid message; and a step of transmitting a message including a result ofthe judgment in said reservation judgment step to a source ordestination of said message for checking whether said predetermined pathis set or not.
 15. A communication message processing method for a nodeor a router provided in a communication system so arranged that aplurality of access routers each constituting a subnet are connectedthrough a communication network and at least one access point forming aunique communicable area is connected to each of said plurality ofaccess routers and a mobile terminal existing in said communicable areamakes a communication with said access router, to which said accesspoint is connected, through a radio communication with said accesspoint, and made to constitute a path related to an additional servicewhen said mobile terminal makes a communication with a predeterminedcommunication terminal, comprising: a reservation judging step of, uponreceipt of a message including a flow identifier and a sessionidentifier, related to a predetermined path, for checking whether saidpredetermined path is set or not, making a judgment as to whether or nota resource reservation is made with respect to said flow identifier andsaid session identifier included in said message; and a transfer stepof, when a judgment in said reservation judging step shows that theresource reservation is made with respect to said flow identifier andsaid session identifier included in said message, adding addressinformation on an interface used for said resource reservation to apredetermined portion of said message and transferring said message. 16.The communication message processing method according to claim 15,wherein said predetermined portion indicates an adding sequence of saidinterface address information.
 17. A communication message processingmethod for a communication node designed to, in a communication systemin which a plurality of access routers each constituting a subnet areconnected through a communication network and at least one access pointforming a unique communicable area is connected to each of saidplurality of access routers, make a communication with a mobile terminalso arranged as to make a communication with said access router connectedto said access point through a radio communication with said accesspoint in said communicable area and designed to be capable ofestablishing a path related to an additional service when making acommunication with said mobile terminal, comprising: a step of, uponreceipt of a message including a flow identifier and a sessionidentifier, related to a predetermined path, for seeking saidpredetermined path, generating a new message including a result of theseeking of said predetermined path in said message to transmit the newmessage as a response to said message.
 18. The communication messageprocessing method according to claim 14, wherein said message forchecking whether said predetermined path is set or not, or said messagefor seeking said predetermined path is a QUERY message or a RESPONSEmessage having an area capable of including a flow identifier and asession identifier which are related to the path.
 19. The communicationmessage processing method according to claim 14, wherein said messagefor checking whether said predetermined path is set or not, or saidmessage for seeking said predetermined path has an area capable ofincluding information on a free resource.
 20. A communication messageprocessing method for a node or a router provided in a communicationsystem so arranged that a plurality of access routers each constitutinga subnet are connected through a communication network and at least oneaccess point forming a unique communicable area is connected to each ofsaid plurality of access routers and a mobile terminal existing in saidcommunicable area makes a communication with said access router, towhich said access point is connected, through a radio communication withsaid access point, and made to constitute a path related to anadditional service when said mobile terminal makes a communication witha predetermined communication terminal, comprising: a reservationjudging step of, upon receipt of a message including a sessionidentifier related to a predetermined path for checking whether saidpredetermined path is set or not, making a judgment as to whether or nota state exists with respect to said session identifier; and atransmission step of, when said reservation judging step shows that saidstate does not exist with respect to said session identifier,transmitting said message toward said predetermined communicationterminal.
 21. A communication message processing method for a node or arouter provided in a communication system so arranged that a pluralityof access routers each constituting a subnet are connected through acommunication network and at least one access point forming a uniquecommunicable area is connected to each of said plurality of accessrouters and a mobile terminal existing in said communicable area makes acommunication with said access router, to which said access point isconnected, through a radio communication with said access point, andmade to constitute a path related to an additional service when saidmobile terminal makes a communication with a predetermined communicationterminal, comprising: a reservation judging step of, upon receipt of amessage including a session identifier related to a predetermined pathfor checking whether said predetermined path is set or not, making ajudgment as to whether or not a state exists with respect to saidsession identifier; a reservation judging step of, upon receipt of amessage including identification information for specifying a flow and asession identifier related to a predetermined path for checking whethersaid predetermined path is set or not, making a judgment as to whetheror not a state exists with respect to said flow specifyingidentification information; and a judgment step of, when saidreservation judging step shows that said state exists with respect tosaid session identifier, making a judgment as to whether or not adifferent adjacent node or router is specified in each of said state andsaid message; and a CRN judging step of, when said judgment step showsthat said adjacent node or router is specified, making a judgment thatit is a crossover node.
 22. The communication message processing methodaccording to claim 21, comprising a notification step of, when said CRNjudging step shows that it is a crossover node, issuing a notificationto the effect that it is a crossover node, to a predetermined node. 23.The communication message processing method according to claim 21,comprising a step of, in a state where said node or said routerconstituting said path related to said additional service has a flowidentification list for storing correspondence relationship between eachresource and information for specifying a flow, adding or deleting saidflow specifying information on said path related to said additionalservice, which goes through it, to or from said flow identificationlist.
 24. The communication message processing method according to claim23, comprising an updating step of, when said CRN judging step showsthat it is a crossover node, transmitting, toward said communicationterminal, a message for adding information, which is for specifying anew flow, to said flow identification list in which the resource forsaid predetermined path is allocated with respect to each receiving nodeor router.
 25. A communication message processing program for executingthe communication message processing method according to claim 10through the use of a computer.
 26. The communication handover methodaccording to claim 4, comprising: a step in which said mobile terminalspecifies an access router having said different access point as afollowing on the basis of said information on said different accesspoint received in said reception step; a step of acquiring informationon said access router having said different access point as a following;and an address generating step of generating address informationavailable in said subnet, to which said access router pertains, on thebasis of said information on said access router having said differentaccess point as a following.
 27. The communication handover methodaccording to claim 5, comprising: a step in which said mobile terminalspecifies an access router having said different access point as afollowing on the basis of said information on said different accesspoint received in said reception step; a step of acquiring informationon said access router having said different access point as a following;and an address generating step of generating address informationavailable in said subnet, to which said access router pertains, on thebasis of said information on said access router having said differentaccess point as a following.
 28. The communication handover methodaccording to claim 4, wherein said additional service is a QoSassurance.
 29. The communication handover method according to claim 5,wherein said additional service is a QoS assurance.
 30. A communicationhandover program for executing the communication handover methodaccording to claim 4 through the use of a computer.
 31. A communicationhandover program for executing the communication handover methodaccording to claim 5 through the use of a computer.
 32. Thecommunication message processing method according to claim 15, whereinsaid message for checking whether said predetermined path is set or not,or said message for seeking said predetermined path is a QUERY messageor a RESPONSE message having an area capable of including a flowidentifier and a session identifier which are related to the path. 33.The communication message processing method according to claim 17,wherein said message for checking whether said predetermined path is setor not, or said message for seeking said predetermined path is a QUERYmessage or a RESPONSE message having an area capable of including a flowidentifier and a session identifier which are related to the path. 34.The communication message processing method according to claim 15,wherein said message for checking whether said predetermined path is setor not, or said message for seeking said predetermined path has an areacapable of including information on a free resource.
 35. Thecommunication message processing method according to claim 17, whereinsaid message for checking whether said predetermined path is set or not,or said message for seeking said predetermined path has an area capableof including information on a free resource.
 36. A communication messageprocessing program for executing the communication message processingmethod according to claim 14 through the use of a computer.
 37. Acommunication message processing program for executing the communicationmessage processing method according to claim 15 through the use of acomputer.
 38. A communication message processing program for executingthe communication message processing method according to claim 17through the use of a computer.
 39. A communication message processingprogram for executing the communication message processing methodaccording to claim 20 through the use of a computer.
 40. A communicationmessage processing program for executing the communication messageprocessing method according to claim 21 through the use of a computer.